Source: https://www.scribd.com/document/340094124/Apta-Ss-Ccs-Rp-002-13
Timestamp: 2018-08-17 00:43:41
Document Index: 109578315

Matched Legal Cases: ['art 2', 'art 2', 'art 3', 'art 3', 'art 2', 'art 1']

Apta Ss Ccs Rp 002 13 | Threat (Computer) | Online Safety & Privacy
Uploaded by aqib ali
APTA STANDARDS DEVELOPMENT PROGRAM APTA-SS-CCS-RP-002-13
RECOMMENDED PRACTICE Published June 28, 2013
American Public Transportation Association Control and Communications
1666 K Street, NW, Washington, DC, 20006-1215 Security Working Group
Securing Control and Communications
Systems in Rail Transit Environments
Part II: Defining a Security Zone Architecture for Rail Transit
and Protecting Critical Zones
Abstract: This document covers recommended practices for securing control and communication systems in
rail transit environments.
Keywords: communications based-train control (CBTC), control and communications security,
cybersecurity, positive train control (PTC), radio, rail transit vehicle, SCADA (supervisory control and data
acquisition), train control, signalling
Summary: This Recommended Practice is Part-II in a series of documents to be released. Part-I released in July 2010
addresses the importance of control and communications security to a transit agency, provides a survey of the various
systems that constitute typical transit control and communication systems, identifies the steps that an agency would fol-
low to set up a successful program, and establishes the stages in conducting a risk assessment and managing risk. Part-II
presents Defense-In-Depth as a recommended approach for securing rail communications and control systems, defines
security zone classifications, and defines a minimum set of security controls for the most critical zones, the, SAFE-
TY CRITICAL SECURITY ZONE (SCSZ) and the FIRE, LIFE-SAFETY SECURITY ZONE (FLSZ). Later parts will cover rec-
ommended practices for less critical zones, the rail vehicles, and provide other guidance for a transit agency.
Scope and purpose: This Recommended Practice is not intended to supplant existing safety or security
standards or regulations. It is instead intended to supplement and provide additional guidance. Passenger
transit agencies and the vendor community now evolve their security requirements and system security
features independently for most of the systems listed above. The purpose of this Recommended Practice is to
share transit agency best practices; set a minimum requirement for control security within the transit industry;
provide a guide of common security requirements to control and operations systems vendors; adopt voluntary
industry practices in control security in advance and in coordination with government regulation; and raise
awareness of control security concerns and issues in the industry.
This Recommended Practice represents a common viewpoint of those parties concerned with its provisions, namely,
transit operating/planning agencies, manufacturers, consultants, engineers and general interest groups. The
application of any standards, practices or guidelines contained herein is voluntary. In some cases, federal and/or state
regulations govern portions of a transit system’s operations. In those cases, the government regulations take
precedence over this standard. APTA recognizes that for certain applications, the standards or practices, as
implemented by individual transit agencies, may be either more or less restrictive than those given in this document.
© 2013 American Public Transportation Association. No part of this publication may be reproduced in any form, in an electronic
retrieval system or otherwise, without the prior written permission of the American Public Transportation Association.
1.1 Intent of the series ........................................................................ 1
1.2 Parts of the series ......................................................................... 1
1.3 Background .................................................................................. 2
The American Public Transportation 2. The need for cybersecurity in rail transit control systems ............ 4
Association greatly appreciates the
contributions of the following 2.1 Overview...................................................................................... 4
individuals, who provided the primary 2.2 Challenges.................................................................................... 5
effort in the drafting of this 2.3 Where do the risks lie? ................................................................ 6
2.4 Comparison of enterprise IT with industrial control systems ...... 8
At the time this standard was
completed, the working group
included the following members: 3. Cybersecurity approach .................................................................... 9
Chuck Weissman, Chair
3.1 Introduction.................................................................................. 9
David Teumim, CISSP, Facilitator 3.2 Defense-in-Depth (layered defense) .......................................... 12
John Moore, Secretary 3.3 Detection-in-Depth .................................................................... 14
Leigh Weber, CISSP, Editor
3.4 Cybersecurity risk zones ............................................................ 15
David Trimble, Assistant Editor
3.5 Defense-in Depth for transportation systems............................. 18
3.6 An example transit system ......................................................... 19
Kevin Garben 3.7 Applying Defense-in-Depth to a model transit system .............. 20
John Weikel 4. System security and minimum controls for Safety Critical Zones
Darryl Song 29
Henry Zhou 4.1 Legend ....................................................................................... 29
4.2 Overview.................................................................................... 30
Andrey Milojevic 4.3 Controls ..................................................................................... 34
5. Applying security controls to zones .............................................. 58
5.1 Safety-critical signaling ............................................................. 58
5.2 Safety-critical Fire Life Safety .................................................. 58
6. Preview of the Recommended Practice series, Part III ................ 59
APTA Standards Project Team
Martin Schroeder, MSME, PE, 6.1 Protecting the OCSZ .................................................................. 59
APTA Chief Engineer 6.2 Securing the train line control and communications.................. 60
Kevin Dow, APTA Program Manager 6.3 Attack modeling for transit control and communications systems
Samantha Smith, APTA Program
Appendix A: Control and communications system account
worksheets ............................................................................................ 61
Appendix B: Out-of-Scope Item Discussion ............................................ 65
References ............................................................................................ 66
Definitions ............................................................................................. 68
Abbreviations and acronyms .............................................................. 71
© 2013 American Public Transportation Association | ii
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical
Defining a Security Zone Architecture for Rail
Transit and Protecting Critical Zones
This Recommended Practice is Part II in a series of documents to be released. Part I, released in July 2010,
addresses the importance of control and communications security to a transit agency, provides a survey of the
various systems that constitute typical transit control and communication systems, identifies the steps that an
agency would follow to set up a successful program, and establishes the stages in conducting a risk
assessment and in managing risk. Part II presents “Defense-in-Depth” as a recommended approach for
securing rail communications and control systems, defines security zone classifications, and defines a
minimum set of security controls for the most critical zones, the safety-critical security zone (SCSZ) and the
fire, life-safety security zone (FLSZ).Part III will cover recommended practices for less-critical zones and the
rail vehicles and provide other guidance for a transit agency.
1.1 Intent of the series
The intent of this document is to provide guidance to transit agencies on securing control and communications
systems for their rail environments. This Recommended Practice spearheads an effort within APTA to extend
cyber security best practices to the transit industry.
It represents the contribution of “leading-edge” information from transit agencies that already have a control
security program, as well as recommendations from the U.S. Department of Homeland Security (DHS), the
Transportation Security Administration (TSA), the National Institute of Standards and Technology (NIST),
vendors who serve the transportation and IT communities, as well as thought leaders in cybersecurity. APTA
intends for this Recommended Practice series to serve as a guide for transit agencies to develop a successful
and comprehensive cybersecurity program.
This Recommended Practice is not intended to supplant existing safety or security standards and regulations.
This document, instead, provides an overview of the need for control and communications protection, and it
fills-in potential gaps in current standards and regulations.
1.2 Parts of the series
Due to the comprehensive amount of information to be conveyed, this Recommended Practice series is
divided into multiple parts:
© 2012 American Public Transportation Association 1
1 Elements. via a powerful network. Organization and Risk Assessment/Management Part I addresses the importance of control and communications security to a transit agency. Transit agencies should consider the following questions: y Can a computer or mobile device be used to collect intelligence about the operational network(s)? y Can an outsider use the network to take control of the system(s)? y What can an unhappy insider do to the network? y How can policies. lines of responsibility. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones TABLE 1 List of Recommended Practices Part I Published July 2010 Elements.2. 1. Businesses that do not use Industrial Control Systems (ICS) may replace 100 percent of their systems within a five-to seven-year window. signals. The long design life of highly reliable systems adds another challenge to addressing control and communications security. Preliminary suggestions and some references on how to approach legacy system retrofits for control security are given in Appendix B: of this document. New technologies. and establishes the stages in conducting risk assessment and managing risk. The primary application is intended to be for new rail projects or major upgrades rather than for retrofitting legacy systems. Organization and Risk Assessment/Management Part II This document Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Part III To be determined • Address the Operationally Critical Security Zone • Address Security Zones onboard the Train Set • Attack Modeling for Rail Transit This division of text material parallels the progression of recommended steps a transit agency would follow to develop and implement a control and communications security program. Many of the systems were never envisioned as being interconnected or accessible. Neither the components nor the systems used every day to control trains. have transit agencies interconnecting more of their systems. 1. training and compliance audits help secure the agency’s assets? © 2012 American Public Transportation Association 2 . It also defines a minimum set of controls for the most critical zones. which uses ICS.3 Background Many systems need to interoperate to allow a transit agency to provide service to the public. provides a survey of the various systems that constitute typical transit control and communication systems. directly or indirectly. controls and communications were designed with an organized set of cybersecurity criteria anticipating today’s cyber threats. rarely replaces all of its systems. identifies the steps that an agency would follow to set up a successful program. combined with the pressure to be more cost-efficient.2. which are the safety-critical security zone. 1. Transit. and those that are replaced may last much longer than 30 years.2 Defining a Security Zone Architecture and Protecting the Safety-Critical Zone Part II (this document) will assume that the agency has completed the risk assessment and risk management steps of Part I and covers how to define a security architecture for control and communications systems based on the Defense-in-Depth model.
3.. NIST. physical security knowledge. 1. it provides strategic recommendations for Chief Information Officers and decision makers regarding business cybersecurity. (e.1.g. Volpe National Transportation Systems Center [Volpe-DOT]). fare collection and general cybersecurity technologies. Specifically. © 2012 American Public Transportation Association 3 . transit vendors. and logical/administrative security.3.2 Control and Communications Security Working Group The Control and Communications Security Working Group develops APTA standards for rail system control and communications security. the John A. FIGURE 1 The APTA Total Effort in Transportation Cybersecurity 1.3. the Institute of Electrical and Electronics Engineers (IEEE).1.1 APTA’s approach APTA has divided the cybersecurity effort into two teams (see Figure 1): y The Enterprise Cybersecurity Working Group y The Control & Communications Security Working Group (CCSWG) The CCSWG draws upon existing standards from the North American Electric Reliability Corporation’s Critical Infrastructure Protection program (NERC-CIP). ISA. government departments. information systems. TSA. and consultants participate in defining and reviewing this Recommended Practice. DHS. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones y How can software change management lessen the chances of software configuration problems? y What could a computer virus do to your computer systems? 1. Additional subject matter experts (SMEs) from transit agencies.1 Enterprise Cybersecurity Work Group The Enterprise Cybersecurity Work Group develops APTA standards pertaining to mass transit cybersecurity.
road crossings. power stations. stations. maintenance yards. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 2. The systems that have been used to control and communicate are located along the routes in wayside bungalows. refueling depots. storage depots. including the following: y access control systems y advertising y closed-circuit television (CCTV) y control and communication y credit card processing y detection systems for environmental threats (CO. escalators. There are also key parts of the control system buried under or alongside the rail lines and signals that are transmitted in the rails or via specialized aerial paths. poisons) y emergency communications y emergency notification y emergency ventilation systems y fare sales/collection y fire detection/alarms/fire suppression y grade crossings y lighting y passenger information systems y people-moving systems (elevators. equipment storage yards/parking lots.1 Overview A transit agency is a very complex organization that has equipment that moves along railroad tracks. people movers) y police dispatch y pumping systems y signals and train control y ticketing systems y traction power y vertical lift devices (elevators. CO2. local control rooms and operations control rooms. © 2012 American Public Transportation Association 4 . escalators) y vital communication-based train control (CBTC). The need for cybersecurity in rail transit control systems 2. tunnels. signal towers. A transit agency has to combine dozens of systems. automatic train protection (ATP) and signaling This Recommended Practice characterizes these systems with respect to personnel and passenger security.
2..2 Challenges Transit agencies have spent anywhere from dozens to more than 100 years running their systems and have dealt with a vast array of issues and threats with an excellent record of safety.2.” i. Enterprise Zone schedule systems Communications with the Internet. there is a tendency to use the same physical communications conduits and. unencrypted commands and text—are also avenues that may be used to usurp control of a control system. for various operations.Critical Security Zone (SCSZ) Field signaling and interlocking Fire. on-time performance and reliability. Life-Safety Security Zone (FLSZ) Fire detection/suppression Operationally Critical Security Zone Traction power SCADA Fare systems. Transmission Control Protocol/Internet Protocol (TCP/IP) or a similar networking standard. measured in decades. Business systems can be fully replaced in several years under ordinary replacement schedules. NIST and related documents. many of these systems did not have any need or method to communicate with each other. This standardization gives new capabilities. The challenge today is to add cybersecurity awareness and cyber defense measures to the transit agency culture in the same manner that safety has been added to the culture of manufacturing and transportation. The connections between and among them were usually direct connections such that one wire connected to another device without any sharing communications—except the cable that the wire was enclosed in. It also gives rise to unanticipated attack paths on these key systems. accounting systems. This Recommended Practice is designed to help transit agencies identify their risk to cyber-attack and to augment the knowledge found in other DHS. not years. Today’s environment has changed so that the communication between and among devices is digital via Ethernet.e. business partners. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones TABLE 2 Zone Names Importance Zone Example System Most Safety Critical Safety.2. 2. External Zone Most Public vendors and others In the past. This will reduce the risks to transit agencies and their supplier base from cybersecurity incidents and possible liability should an incident take place.2 Systems with long life cycles Some elements of transit systems have very long lives. This reuse may create vectors for cyber-attack. It explores the unique aspects of transit and discusses how to apply well-defined cybersecurity techniques to keep transit agencies’ systems operational and under control. turnstiles. Transit systems. are not replaced in significant ways for decades.1 Shared infrastructure Due to the vast distances that transit agencies traverse. Other shared infrastructure—such as broadcasting via radio signals over well-known frequencies and transmitting “in the clear. 2. in some cases use multiplexing technologies. © 2012 American Public Transportation Association 5 . however. ISA.
Attacks. 2.2. firewall and other current cyber-defense technologies that may inject delays in communications or block execution of programs carry the risk of unintentionally disrupting system functions and therefore must be carefully evaluated. the security of control systems could be addressed by carefully limiting physical access to elements of the control system. terminals and control computers. if successful. 2. Servers and workstations both use available open system architectures and commercial-off-the-shelf software. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 2. Information and products are widely available to the general public for almost every component of a modern control system.3. and relying on obscurity.2 Malware infection methods Vulnerabilities exist even for unconnected systems through the following methods of indirect malware infection: TABLE 3 Malware Infection Methods Undesirable software/functions may already be embedded or pre-loaded Supply chain in off-the-shelf equipment. 2. Control systems are also expected in many cases to have no downtime. and could not be stored.3.1 Connectivity changes Until recently.3 Real-time and time-sensitive information Control systems by nature have real-time and time-sensitive requirements that are not common in traditional IT systems. could not easily propagate. Servers and workstations utilize standard off-the-shelf computer hardware and operating system technology. Irresponsible use of portable media (USB) for unauthorized data/program Human factors transfer. such as IT and business systems or the outside world. Antivirus. Modern control systems components and architectures are virtually indistinguishable from business information system components and architecture. Inadequate physical security Who is touching or can touch “secure” equipment? Inadequate configuration management Unknown connections may be made through a change to the system.3 Where do the risks lie? Transportation agencies traditionally considered their communications and control systems to be proprietary (security by obscurity) and not to be connected to the outside world and therefore assumed to be secure. © 2012 American Public Transportation Association 6 . There are paths from one system to another that may not be anticipated Unexpected/indirect connections or understood. To compromise the system would require specialized knowledge and access to locked equipment rooms. Systems were primarily implemented using proprietary hardware and software communicating non-standard protocols over privately owned modem lines and had no practical connections to other systems. TCP/IP and other published industry standard protocols (often not secured) are used for inter-process and remote site communications over wire and wireless connections. This assumption and attitude is no longer valid or acceptable. would generally be isolated to one remote site. Vendors may deliver infected or un-validated software. such as modems. whitelisting.
TABLE 5 Transit Control System Priority Confidentiality Lower Importance Integrity HIGH IMPORTANCE Availability HIGH IMPORTANCE © 2012 American Public Transportation Association 7 . If the information is not available. Wide geographic area deployment of equipment. Web-enabled public information systems and remote business partner interfaces are a growing trend. Connection to the outside world and corporate business and enterprise systems is inevitable if not already in existence. it is always important to know where the system’s trains are and that the switches and crossing gates are in their correct positions. sometimes in unprotected public locations. salaries or medical information to be made public. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Extensive use of open and off-the-shelf technologies expose systems to vulnerabilities once limited to traditional IT systems and personal computers. The company may ask its customer to call back at another time. Open standards and proliferation of readily available tools (both legitimate and malicious) make things easier for people with bad intent. so that trains can be stopped or started and so that crossing gates go up and down appropriately. 2. Agencies can no longer rely on proprietary networks. and its confidentiality may be the least important. One only needs to gain access and then utilize available tools. that it is the correct and complete set of information—in other words. A business also needs to know that when it gets the information. There are cases where integrity is as important as or more important than availability. y Business system: The business is most concerned about keeping information confidential. TABLE 4 Business IT Priority Confidentiality HIGH IMPORTANCE Integrity HIGH IMPORTANCE Availability Lower Importance y Control system: The control system needs information to be available so that calculations can be made. that is. it does not want private information such as social security numbers. Agencies are facing increasing pressure from both inside and outside the organization to obtain and share data. that the information has integrity.3. For example.3 Different approaches to cyber security There is a fundamental difference in approach to protecting a business information system compared with an industrial control system (compare Table 4 and Table 5). hardware and software for protection. The information’s integrity is important. It is no longer necessary to hack the system. that is inconvenient but not a critical problem. presents additional security vulnerability to transportation systems. credit card numbers.
are for systems that are meant to run uninterrupted 24 hours a day.C. assets or individuals. however it is being practiced more during hardware/software development lifecycle. 1 FIPS Pub 199. Standards for Security Categorization of Federal Information and Information Systems 2 US-CERT. organizational operations. and availability. effect on organizational privacy and proprietary organizational assets or organizational assets or operations. of information could be of information could be of information could be includes ensuring expected to have a limited expected to have a serious expected to have a severe information non-repudiation adverse effect on adverse effect on or catastrophic adverse and authenticity. integrity. individuals. including means adverse effect on adverse effect on or catastrophic adverse for protecting personal organizational operations.S. organizational individuals. individuals. organizational operations.S. Sec. assets or individuals. organizational individuals.) TABLE 6 FIPS Cyber Security Categorization Security Objective Low Moderate High Confidentiality: Preserving The unauthorized disclosure The unauthorized disclosure The unauthorized disclosure authorized restrictions on of information could be of information could be of information could be information access and expected to have a limited expected to have a serious expected to have a severe disclosure.[44 U. organizational operations. y ICS systems have a very long life cycle measured in decades. organizational information. 3542] expected to have a limited expected to have a serious expected to have a severe adverse effect on adverse effect on or catastrophic adverse organizational operations. organizational operations.[44 information system could be information system could be information system could be U.[44 U.S. compared with many IT components that last only three to eight years. Availability: Ensuring The disruption of access to The disruption of access to The disruption of access to timely and reliable access to or use of information or an or use of information or an or use of information or an and use of information.. effect on organizational organizational assets or organizational assets or operations. Sec. individuals.4 Comparison of enterprise IT with industrial control systems Figure 2 summarizes several cyber security topics as they apply to traditional IT systems and industrial control systems.us-cert. 3542] organizational assets or organizational assets or operations.. assets or individuals.C. (Please note that the FIPS table was developed for business systems. 2.http://www. separately..2 The key differences between enterprise IT and ICS are the following: y Difficulty of testing and applying patches to ICS because those systems affect life safety and. February 2004.pdf © 2012 American Public Transportation Association 8 . individuals.C. effect on organizational Sec.gov/control_systems/practices/documents/Defense_in_Depth_Oct09. 3542] Integrity: Guarding against The unauthorized The unauthorized The unauthorized improper information modification or destruction modification or destruction modification or destruction modification or destruction. y Note that “Secure Systems Development” is usually not an integral part of industrial control systems development. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Table 61 summarizes the potential impact definitions for each cyber security objective—confidentiality.
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones FIGURE 2 Comparison of Enterprise IT with Industrial Control Systems NOTE: Compare the business / enterprise point of view (middle column) with the Industrial Control System (right column) 3. for the purposes of this document. Cybersecurity approach 3. is defined as the means to reduce the likelihood of success and severity of impact of a cyber-attack against transportation sector control systems through risk-mitigation activities. © 2012 American Public Transportation Association 9 .1 Introduction Cybersecurity.
2. Traction power systems: For electrified railways 3. control the speed of or stop the train. what. A rail transit system is comprised of several components: 1. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. connects to a communication network via a wired or wireless connection. people. it would not make sense to protect all things at the same level. devices and processes that are most important or are most easily corrupted. determine who. policies and processes that work together to transport people safely and in a predictable manner. The following are the key parts of protection: y Prevention: Keep anyone or anything from tampering with the system y Tamper detection: Detect when an unauthorized change has been or is being made y Auditable: If someone does tamper with the system. and. Train-sets: which may have separate locomotives. communicates with digital devices. which includes switches to change track/guide and many other devices built into the track/guide to ensure wheel placement. In addition. at grade. Stations: Below ground. when and how y Tamper detection and auditability ensure appropriate personnel are notified of unauthorized or abnormal activity and can respond in a timely manner to take action as required In addition. end of track bumpers. A system may be a mix of these station types. crews. Communications: Between and among operating trains. or above ground. where. transit agencies need to identify those systems. etc. There are many protections in place today. road crossings and speed controls.1 What needs protection? Transit systems are complex and consist of equipment. Notification methods: Signs. 5. Control signaling system: Signals (if present). transit agencies need to ensure that trains run on their prescribed paths and that all crossings are properly controlled and protected. horns and other types of displays 6. Another goal is to reduce the likelihood of human error. and to ensure that these systems cannot be directly controlled by anyone other than their owner/operator. 3. these may be powered by different methods.1. Rail systems have many levels of safety built into them via redundant circuits. © 2012 American Public Transportation Association 10 . fail-safe control systems (vital logic). the most critical systems to protect are those that involve the highest risk to life and property: such as the control and communication systems that let the train or train operator start. and other mitigations. Transportation: Rail(s) that guide the train-set. For rail. In general any device that uses a digital processor. The question becomes how best to prioritize a transit agency’s protection method. mostly focused on the physical security of the passengers and the transit system’s assets. public address (PA) systems. station attendants. police and the operations center 4. or that can be programmed could be considered for protection. electronic signs.2 Protection philosophy Even with unlimited resources. The role of cybersecurity is to ensure that these existing systems cannot be duped into making a wrong decision. such as forgetting to apply an update or applying an incorrect update to a part of the system.1. 7.
a cybersecurity program that addresses: threats. monitoring and detection methodologies. when the wrong person is given access to an important system. malware or a phishing type attack (e.2 Cyclical review Cybersecurity is a rapidly changing set of threats. as well as unofficial sources that forewarn about potential threats. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Figure 3 shows which systems need the most protection and which need the least.2. DHS Surface Transportation Information Sharing and Analysis Center [ST-ISAC]).g. and the ability to be audited to check for compliance via logs and change-management systems. people don’t pay attention to what they are doing. for information on starting a cybersecurity program. The people who want to disrupt or access transit systems keep coming up with new ways to cause harm. mitigations. Agencies need to be connected to sources of official (e. “Securing Control and Communications Systems in Transit Environments” (APTA RP-CCS-1-RT-001-10). It is very important that a transit agency’s cybersecurity culture stay on top of the evolving threat landscape in order to protect its passengers. staff and assets..g. FIGURE 3 Protection Priorities 3. “hacktivists” and state- sponsored cyber-war groups. It is based upon the probability of a successful attack and the adverse impact such an attack would have. an assessment of cybersecurity threats. the software/firmware update process. This requires an awareness program. 3.1. a training program. malicious groups including organized crime.1 Cybersecurity culture Many cybersecurity breaches occur accidentally. A program is needed that routinely examines: © 2012 American Public Transportation Association 11 . a reduction of the attack surface (the number of places and ways someone can attack transit systems). clicking on a link in an email). or outsiders are given an opening into computer systems via a virus.2. Please see Part I of this series. There is a growing threat from focused. Just as transit agencies have created a safety-centric culture—saving lives and reducing accidents and accident severity—they need to foster and create a cybersecurity culture.1.
The strategy recommends a balance between the protection capability. cost. y strengths. It should control what is going on and who has access and privilege to monitor.1 Types of threats Simply put. For a transit agency to successfully use the Defense-in-Depth model. y allowing security policies and procedures to better align with agency organizational structure. A zone has a boundary or an interface point that protects information and transactions as they move across zone boundaries (electronic security perimeters or ESPs. This practice is known as the “Principal of Least Privilege”. It is a best-practices strategy in that it relies on the intelligent application of techniques and technologies that exist today. This strategy was conceived by the National Security Agency (NSA) and is an adopted recommended practice of the Department of Homeland Security Control Systems Security Program (DHS-CSSP). operate and react to changing conditions. see Definitions). Defense-in-Depth is the recommended strategy for securing communications and control systems for the transportation sector. configured properly and working as designed. A zone may be contained within another zone or a zone may be parallel and separate from another zone.2. processes and operations. Transit agencies need to combine Defense-in-Depth with Detection-in-Depth. then the least amount of privilege is given to the least amount of people. NOTE: Electronic Security Perimeter (ESP) Adapted from NERC –CIP electric power regulations. and y resources.2 Defense-in-Depth (layered defense) In order for an agency to protect it’s most valuable and important assets. and an audit program to ensure that all parts of the layered defense are in place. performance and operational considerations. 3. © 2012 American Public Transportation Association 12 . It is a best practice to start from the assumption that all access is denied until a valid reason is given. It effectively addresses many cybersecurity scenarios by: y increasing the amount of time and number of exploits needed to successfully compromise a system. These reviews should be “built into” internal procedures. 3. y increasing the likelihood of detecting and blocking attacks. it is a logical perimeter drawn around electronic assets in a security zone to separate it from other zones. giving each zone its own defensive layer. The program’s goals are to define. it needs to define zones. Defense-in-Depth implements multiple levels of security to provide layers of backup in the event a security control fails or an attempt is made to exploit new or unaddressed vulnerabilities. and y directly supporting the identification and implementation of cyber security risk (or impact) zones. a transit agency needs to ensure that no one can interfere with its normal and proper operation. protect from and reduce the probability of a cybersecurity incident. y weaknesses. it is thought safest to have layers of defenses so that outsiders have no direct access to an agency’s most valuable assets. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones y threats. Defense-in-Depth is a practical strategy for achieving cyber security objectives in today’s highly networked environments. a compliance program.
2. a transit agency should restrict each group to its own equipment and systems. © 2012 American Public Transportation Association 13 . Such an insider has plenty of information about the transit agency’s operation. it should either be removed or locked down so that an attacker cannot use it as an entry or control point. then the control system can be compromised by the insider – unwittingly.1.2. such as a pass phrase or a password into a system before being able to access the system and make the change.) may unintentionally compromise a system because they have been manipulated (social engineering attacks). 3. use a special key or enter a special value. Each of these software applications needs to be monitored.3 Sources of threats An insider (employer.2. Examples: y An open-source web-server y File-transfer utilities y Remote management utilities These features may be important for the initial configuration of the device.3. if the “convenience” application is not required.1 Accidents and errors To reduce the chance of an innocent mistake becoming a serious problem. or their computer or device has become compromised.2 Embedded/included software Suppliers often include or rely upon software that they did not develop or do not maintain. (Note: see Section 4. To make our systems safe it must be acknowledged that we are all human. while others may intend to directly take control of systems or change the information displays in order to cause an accident or catastrophe.control 4. Threats also can come from outside—anyone from a teenager to a competitor to organized crime to a state- sanctioned cyber-war group.13 for a further discussion on patch management) A transit agency must know if its vendor will support patched versions of the “convenience” applications. etc. In general. such as convenience. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. logging and other procedures to ensure that people do their job. or they may be present for other reasons. If an insider’s equipment is not properly protected. and it must also know the vulnerabilities that will exist if it does nothing. attacks come in many forms. contractor.2. that they are reminded when they are accessing critical equipment or systems. . so a good system builds in controls. A disgruntled insider is one common form of an attack and is often the hardest one to protect against. Some may attempt to breach security just to gather information. and his or her colleagues are often willing to “bend” the rules on their behalf. Mistakes are inevitable.2 Intentional attacks Whether from a disgruntled insider or from an outsider. or the change management system is lacking proper controls. 3. 3. configured and patched as necessary. They may have to show ID.1. and that they are challenged when they try to enter sensitive or secure locations. controlled.
and details of cyber-attacks affecting other industry sectors. Denial of service attack Denial of service attack against a backup network supporting signaling. In many IT environments. the malware makes an outbound 3 A firewall is a dedicated device that adds a layer of security to your network. under Appendix A. © 2012 American Public Transportation Association 14 . The principal of least privilege tells us to first block ALL outbound traffic. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3..2. Polish tram hack in 2007 The Polish tram hack caused injury to 12 people and derailment and damage to four vehicles.3 Detection-in-Depth A key concept that is a companion to Defense-in-Depth is Detection-in-Depth. vulnerabilities and risks and will be introduced in Part III of this series.2. 3. Detection-in-Depth is a way to detect that an intruder has gained access to a transit facility.2. 3. It can do that by analyzing all data packets passing through it and determining which are allowed based upon preset rules. after the malware infects a device.3. More details of these attacks and their consequences.3. the firewall3) have many rules to prevent unauthorized connections into the protected zone. Cybersecurity controls that may be effectively applied to traditional IT systems may not be appropriate for control systems and/or might compromise their function in unexpected and potentially unsafe ways. Malware takes advantage of this lack of protection.g. including the following (see also Section 2.4 Well-known attacks Some examples of cyber-attacks on rail have already been publicly documented. “Different Approaches to Security”): TABLE 7 Well-Known Transportation Cyber Attacks Class 1 freight railway virus This class 1 freight railway virus attack caused a morning shutdown of signaling and attack in 2003 dispatch systems in 23 states east of the Mississippi.6 Attack modeling Attack modeling is an advanced technique for analyzing system threats.5 Managing threats All of the above factors contribute to special security challenges for transit control systems. The firewall’s main objective is to control the incoming and outgoing network traffic. and then create permission for known and necessary outbound connections. the isolation devices (e. but often there are no rules to prevent outbound connections. causing speed restriction on the entire line. Detection methods must be created for each zone and defensive layer. may be found in Part I of this series. also halting Amtrak trains in that area. 3.
a closed environment. The creator then has complete control of the infected machine. which helps run the plant. For the most part. a manufacturing facility has the manufacturing plant where the product is made and the offices where the rest of the work is done. Cybersecurity risk zones (also known as impact zones) segment system functions into distinct impact areas with well-defined data exchanges among them. each architectural zone is managed by a separate business unit and is protected by a dedicated device. 3. Table 8 shows the DHS model of security zones for manufacturing.4. In a simplified model. The following uses much of the language from DHS’s “Recommended Practice: Improving Industrial Control Systems Cybersecurity with Defense-In-Depth Strategies” (October 2009). Different business units may need to establish joint responsibilities in the security management and monitoring of a particular cybersecurity risk zone. Defense-in-Depth prevents this scenario by creating outbound connection rules in the isolation device and blocking such outbound connections. which are used for the business of running the business. It is further recommended that the types of zones be limited in order to simplify the application of consistent controls. and the IT corporate systems. © 2012 American Public Transportation Association 15 . The “closed environment” of the control domains allowed industry to have a level of reliability that permitted the safe and efficient operation of the plant. software and networks into physically distinct areas with well-defined connections between them. This model is for a chemical plant or similar manufacturer. Commonly.1 The DHS manufacturing model of Defense-in-Depth The Defense-in-Depth strategy from DHS is available for manufacturing industries. Cybersecurity risk zones present special planning challenges in that they exist within each architectural zone and potentially across them. as shown by Figure 4. 3. perhaps a firewall or other controlled device. a person would need physical access to the plant and the control equipment to sabotage or modify its normal operation. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones connection to its creator. A successful Defense-in-Depth approach requires agencies to partition control system components and functions into distinct zones based on specific security requirements.4 Cybersecurity risk zones Figure 4 shows an overview of the key elements of a Defense-in-Depth strategic framework for a manufacturing facility. Each zone will require a unique security focus and strategy. The IT systems are roughly divided into the control domain. Architectural security zones segment hardware. A Detection-in-Depth system would also include monitoring and profiling information to detect an unusual connection attempt from the machine and to detect that malware had infected the machine.
such as safety instrumented system. The control system network probably does not have any cybersecurity countermeasures in place. High The simplified IT architecture provided a means for data sharing. Corporate Zone The area of connectivity for corporate communications. peer-to-peer data exchange and other business operations. NOTE: The underlying assumption in the control domain is that all of the components are trusted. and there are few. but it is not expecting sabotage. Safety Zone The area that controls directly and often automatically the devices that control Extremely 4 the safety level of an end device. if necessary. This is not a demilitarized zone (DMZ). © 2012 American Public Transportation Association 16 . The control system tries to detect data transmission errors. data acquisition. This “security by obscurity” model does not address insider threats. Therefore. HMI and basic input/output devices such as actuators and sensors. Operational support and engineering management devices are located in this High 2 zone alongside data acquisition servers and historians. and backup or remote offsite facilities. and IT business system infrastructure Medium 1 components are typical resources in this zone. and y for an attacker to learn about the plant’s IT and control systems and their security. Zone Description Priority Number External Zone The area of connectivity to the Internet. What has changed? The control domain is now connected to the corporate IT infrastructure. organizations that do not have a connection to the Internet. however. Manufacturing/ The area of connectivity where a vast majority of monitoring and control takes Data Zone place. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones TABLE 8 DHS Zone Model for Manufacturing Security Ref. when confronted with problems will alarm and. the security of any given system was based on the fact that few. A control system. This zone is central to the operation of both the end devices and the business requirements of the Corporate Zone. it is conceivable and possible for someone acting remotely to access and modify a control system. in today’s interconnected environment. understood the intricate architecture or the operational mechanics of the resources on the control system local area network (LAN). Email servers. fail-safe. Control/Cell The area of connectivity to devices such as programmable logic controllers Very High 3 Zone (PLCs). Domain Name System (DNS) servers. The merging of a modern IT architecture with a control system is challenging. if any. How does one evaluate the risk and devise reasonable countermeasures to ensure the efficient and safe operation of a plant while still gaining the benefits of a very integrated IT architecture? The goals are to minimize the ability: y for an attack attempt to go undetected. It is a critical area for continuity and management of a control network. if any. y for an attack to be successful. it generally worked well for environments that had no external communication connections. thus allowing an organization to focus on physical security to safeguard their system. peer locations. However. but it is the point of Lowest N/A connectivity that is usually considered untrusted.
• The Control Zone has been divided into Control Room and Field Locations. There are differences in location. FIGURE 4 DHS Defense-in-Depth for Manufacturing The challenge for transit agencies is to take this design approach and apply it to a transportation system. • Various symbols have been modified. • The Safety Zone has a different set of symbols shown. “product” and the overall geographic area served.” It has been modified in these ways: • The External Zone content is highly simplified. © 2012 American Public Transportation Association 17 . APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones NOTE: Figure 4 is based upon the DHS Manufacturing Defense-in-Depth diagram in “Recommended Practice: Improving Industrial Control Systems Cybersecurity with Defense-In-Depth Strategies.
road crossing gates. Cybersecurity adds a new dimension to the security program. advertising displays. and between and among the control and signal devices. Much of the communication needs to be done along long distances and in all kinds of weather. A transit agency needs to communicate with maintenance crews on or near the track. Transit agencies are expert at the physical security aspects of their systems. above ground.5.5. downed trees). a rail system includes self-contained equipment rooms located along the tracks.5. various maintenance and detection devices. and in an electrically noisy environment that is difficult to shield. including lighting. Additional power is required to run all other equipment.2 Communication There are various means of communication among the segments: y wired communication y wireless communication The various types of wiring can be located underground. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. plant growth. the most common difference is the use of floating ground. Also. such as signals. Power is distributed via catenaries or third rail. communications and signals. passenger information displays. known variously as signal bungalows and waysides. © 2012 American Public Transportation Association 18 .1.5 Defense-in Depth for transportation systems 3. There are power feeds from local utilities that need to be coordinated.5.1 Distance A rail system covers vast distances. There are differences between a railroad electrical system and most other commercial systems. emergency information displays. between the train set and the wayside. with engineers/drivers (if applicable).1. and each segment of the rail system has to communicate with its adjacent segments and with the operations control center (and backup operations control center).3 Power A transit system often has its own traction power stations for electricity. 3. and others.1. Stray signals can be anathema to good communication system operation. In addition. or through signals sent directly though the track.1 What is different? There are several differences between a rail transportation system and a single manufacturing site: y distance y communication y power y people y access to property 3. train systems often use a different electrical ground default from all other commercial systems. where line-of- sight communication can be difficult due to nature (snow. track circuits. 3.
1. third rails. wayside equipment and communication bays.5. 3. Transit agencies need to focus on prevention and detection of people accessing key areas.1. There are signals along the track. In a manufacturing environment. etc. There is an operations control center. and their movements can be carefully controlled. and along the track there are signal bungalows to control signals. overhead wiring. cafes. regardless of its size.) that must allow everyone access. 3. there are relatively few people who need to access the site. switches. Transportation system assets. including entrances. public areas. This is a fixed block model that has stations below ground. such as power sources. are out in public. at-grade and elevated.6 An example transit system Consider an example transportation system (Figure 5). the maintenance yard will not be addressed. and they expect and need to be delivered safely. exits. interlocking and road crossings. (For now. such as equipment and power rooms. There is a main line with several stations and a spur with two stations. Physical security exists—much of it to keep the public from dangerous areas. Each station has its own equipment rooms. on the other hand.) © 2012 American Public Transportation Association 19 . tracks.5. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. platforms.4 People Everywhere The purpose of a transportation system is to move people. employee areas and so on. waiting areas and amenities (toilets. There are other areas that need to be restricted. Although a manufacturing plant has people to operate and secure the plant. Transit systems have many large. They are the precious cargo of the system.5 Access to property A manufacturing site. and fares are collected at each station. such as signal bungalows. transportation systems can be a much more compelling target due to the vast number of people who use it and any attack’s immediate impact upon passengers. can for the most part restrict who has access to it through physical means. signaling systems. the path of trains and so on—but it is impossible to keep determined individuals away from the transportation system’s assets.
vending. lighting. It has employees. fare collection systems.7. trash. equipment rooms. locked doors. gas. emergency phones. biological). This discussion will focus on the signals and communications group. seismic.7 Applying Defense-in-Depth to a model transit system In the model transit agency. life safety and the operations group. two lines. vendors and others present on the premises. 3. assume that the staff is also divided into separate divisions or reporting groups. fire response. 3. electrical panels. surveillance systems. passengers. IT. the most critical zones are the SCSZ and the FLSZ.6. it’s time to consider how this system can keep moving people in a predictable and safe manner. hazard detection (fire. In addition. contractors. accounting and many others. system police. traction power systems. regular and emergency communications and much more. This should be considered a fully functioning transportation system. restricted areas. It has parking lots for cars. Although fare systems are important—protecting cash and passengers’ personal identifying information—from the point of control and communications security. water. heat and air conditioning. track maintenance. advertising. and a typical staff organization—is defined. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones FIGURE 5 Example Rail Transit System 3.1 Putting it all together Now that the model transit system—seven stations. smoke and other life safety concerns. (SCSZ is used for train signaling and communications. electric access card areas. ticket sales. FLSZ systems are used to detect and remediate fire. station platforms.) © 2012 American Public Transportation Association 20 . there are other groups for public relations. people movers (escalators/elevators).1 Use of the example system The transportation system shown in Figure 5 will be used as a basis for many of the discussions in this document. announcement and public information displays.
The fare collection people. Life-Safety See Section 3. An important part of an effective cybersecurity program is to give the right people access to the right places and to give them exactly the privilege they need to perform their primary job. the signaling people should not be able to change the fare system. Enterprise Zone The enterprise zone. determining which systems are most critical to the operation. VPN.2 Cybersecurity risk zones for rail transit Table 9 and Table 10 provide two generic models of control and communications security zones.7. Security Zone (FLSZ) Safety Critical See Section 3. should not be able to change the behavior of the signaling and switching control system. accounting and engineering controls (checks and balances) in place.” because each person has the least amount of privilege needed to do his or her job and no more. train control. The group also looked at the people within the organization who are responsible for maintaining and operating the systems. and there are business.3 How were the zones derived and defined? The working group performed a high-level generic risk assessment of the example system.7. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. or corporate zone. a thorough risk assessment considering these unique requirements and resultant zones should be conducted. email.3. and other centralized control hardware and software. remote operations and facilities. transit passenger information system. Each person has exactly the permission needed. where applicable. etc. It is not trusted. central authentication services. hardware and services that are made available to the control system via the agency’s corporate network and includes agency business systems.7.7. Cyber protection of the next two zones is addressed by the APTA Enterprise Cyber Security Work Group. There is a separation of access and a separation of authority between these zones. for example. (An example would be for a full CBTC system). fare collection systems. Likewise. If a particular transit agency has a unique set of requirements and wishes to define control and communications security zones differently. Separation of duties should be in place for each part of the organization. This is often referred to as “least privilege.3. includes. and the equipment from these control center zones extending out to remote facilities such as train stations and trackside equipment. and remote business partners and vendors. © 2012 American Public Transportation Association 21 . Cyber protection of the following three zones is addressed by the APTA Control and Communication Security Working Group TABLE 10 List of Zones (APTA Control and Communications Security Working Group) Operationally Critical The control center zone includes the centralized supervisory control and data acquisition Security Zone (OCSZ) (SCADA). Security Zone (SCSZ) 3. TABLE 9 List of Zones (APTA Enterprise Cyber Security Work Group) External Zone The external zone includes Internet-accessible services. Fire.
How does the agency choose? If the agency has only above-ground train stations with no need for emergency ventilation. These systems should not be in the Enterprise Zone. it may assign ventilation systems to the OCSZ. may be assigned to either the OCSZ or to the FLSZ.7. interlocking and ATP should be in the SCSZ. an agency may choose the appropriate zone. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones The SCSZ contains any system that if “hacked” and modified would cause an immediate threat to life or safety—for instance cause a collision or derail a train.7. Example: Vital rail signaling. it should assign the emergency ventilation portion of the ventilation system to the FLSZ.5 Cybersecurity zones across a large physical space It’s clear that security zones may be spread out across many physical locations. are pre-assigned to a zone and may never be assigned to another zone. protect or inform in an emergency. while the traction power emergency cut-off (blue- light) system and protective relaying should be assigned to the FLSZ. Figure 6 gives a detailed look at the allocation of these security zones across physical locations. due to their nature. © 2012 American Public Transportation Association 22 . based upon the circumstances of its transit system. Examples: y emergency management panel y emergency ventilation systems y fire detection and suppression systems y gas detection systems y seismic detection 3. depending upon their purpose. Examples: y Vital signaling. controlling the power should be assigned to the OCSZ. Ventilation systems. Some functions. 3. For other functions.4 Defining zones (system categories) For each function and system used by a transit agency. For traction power in a station. but if it has below-ground train stations. To be cyber-secure. the transit agency must find a way to implement the security zones across this vast space and to also control the physical access and permissions to these critical systems across the physical locations. the transit agency should assign it to exactly one zone. External Zone or SCSZ. interlocking and ATP The FLSZ contains any system whose primary function is to warn.
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones FIGURE 6 Model Zone Chart for Transit Systems © 2012 American Public Transportation Association 23 .
FIGURE 7 Geographical Dispersion in a Rail System © 2012 American Public Transportation Association 24 . APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Figure 7 illustrates how the SCSZ is connected along various rail lines and that it is separated from the FLSZ/OCSZ/Enterprise Zone in a significant way vis-à-vis control and communications security methods and communication.
Note that the SCSZ and the FLSZ should have separate ESPs. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. © 2012 American Public Transportation Association 25 .7.6 Representation of transit system security risk zones Figure 8 shows our security zones in the aggregate. and how they relate to the functions needed by a typical transit agency. and that each of the other zones need the appropriate level of protection for their zone (a topic that will be addressed in Part III of this series). Electronic Security Perimeters (ESP) as described in Section 4 of this document.
only the most critical systems should be in the most critical zone.6. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones FIGURE 8 Transit System Security Risk Zones 3. To ensure a properly protected system.7.1 System category rules There is a careful balance between putting too much into the more secure zones while at the same time not giving extra opportunity for an attack. © 2012 American Public Transportation Association 26 .
1 Operationally Critical Security Zone y Should include: traction power. generic.7. Enterprise.7. but it must be done where necessary to achieve an acceptable level of risk.7 General rules This Recommended Practice gives a model for determining the zone for each function or process based upon the generic model system. OCSZ. Warning: Do not combine the functions and services of one zone into another zone without proper mitigations. ATP y Should not include: anything from other zones: External. communications and related features that. transportation system. 3. It may make it impossible to enforce the necessary most-restrictive security controls across the entire zone to keep the transit system safe and secure. it is not good security practice to implement a clearly non-safety critical function into the SCSZ. biologics. This may create covert channels that an attacker can use to control an agency’s systems. Life-Safety Security Zone y Should include: fire.7.3 Safety Critical Security Zone y Should include: all “vital” systems for signaling and interlocking.7. Enterprise Zone 3. External Zone or Enterprise Zone 3. FLSZ © 2012 American Public Transportation Association 27 . For agencies with different system requirements. may need to be included in the more secure zone. Perceived economies of scale or other business decisions often do not fully account for the risk and cost of mixing functions.7. ATS.2 Fire. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones There are supporting systems. In all cases the transit agency should document its choices and rationale. External Zone. hazard. dispatch y Should not include: anything from SCSZ. after careful risk analysis. Putting something into a more secure zone should not be done lightly. monitors for seismic. For example. NOTE: This Recommended Practice is based upon a typical.7.7. poison gas. traction power emergency shutdown systems y Should not include: anything from SCSZ. 3. a separate risk assessment resulting in modified zone definitions should be completed and documented.
© 2012 American Public Transportation Association 28 .8 An example of systems and the zone they belong in Table 11 shows which zones make sense for some common categories.7. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 3. clearly communications is involved in every zone. So as a category. TABLE 11 Zone Matrix Zones Category External Enterprise OCSZ FLSZ SCSZ Vital signaling ONLY Fare handling ONLY Fire and safety ONLY Traction power SCADA (non- ONLY emergency) Non-emergency ventilation Offices Stations Emergency ventilation ONLY In a networked system. communications cannot be restricted to solely one zone. This document gives guidance on how to segregate network traffic and gives several techniques to consider for separating communications functions into zones.
1 (1. Figure 9 explains the meaning of the headings. 3. and that is it will be developed after Part 2 is issued. Each minor revision will increment the value by . Aud (audience):Who must follow or use this control • TA: Transit Agency • VEND: Vendor • BOTH: Applies to everyone When: When does the control apply? • Now: Applies at date of issue • To Be Dev: To be developed (See note below) Ref # Version Aud. electronic security perimeters. It is included in this document so the rail transit industry may start thinking about how this control could be developed.0. and how the security controls in this document are being met as records for security auditing and assessment.2). Each page has this format. When TITLE: [Title of control] Reference: CONTROL: [Details of control] Primary: NOTES: • The “To be developed” designation for a security control indicates the security control text is informative.1 Legend The following pages expand and explain the recommended controls. © 2012 American Public Transportation Association 29 . System security and minimum controls for Safety Critical Zones 4. This will not change across versions Version (version number): Initially 1. including system drawings with de- scription of security zones.0).0. 1.1. or in a future revision of Part 2. Major revisions will increment the whole number (2. • Transit agencies and vendors should keep adequate system documentation. FIGURE 9 Recommended Controls Legend Ref #: Reference code. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. It will be fully developed and then included in Part 3 of this Recommended Practice series (see Section 6.0).
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. All network-routable interfaces connecting the SCSZ or FLSZ B Both with a less-critical security zone should use an isolation device Now (defined below) to ensure security separation.3 should be required to connect C Both Now physical separate SCSZ zones when using wide area networks (WANs) or local area networks (LANs). Separate fiber-optic strands or other acceptable isolation methods per control 4.2 Overview To partition the system according to the rules of the previous section. the security controls in Table 12 should be applied. TABLE 12 Overall Controls Applies References and Ref Description When to Apply to: Citations The transit agency should draw electronic security perimeters NIST 800 -18. Generic drawings are supplied to indicate where each control should be applied. 82 A Both around the SCSZ and FLSZ to separate them from each other Now and from the other zones.2. 53. © 2012 American Public Transportation Association 30 .
protect or inform in the event of an emergency. or serious malfunction. Measures of effectiveness y Audit of systems during design. emergency ventilation equipment.0 TA Now Reference: SP 800-53 CONTROL: The transit agency should draw electronic security Primary: perimeters around the SCSZ and FLSZ to separate them from each other and the other zones. Examples y Acceptable: y Not acceptable: © 2012 American Public Transportation Association 31 .2. higher security zones need to be behind perimeters in order to segregate it from lower zones. Sabotage. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. Discussion The following definition will serve to illustrate the systems included in SCSZ and FLSZ classification: y SCSZ: A system that if inadvertently or deliberately sabotaged could cause an immediate threat to life safety (for example. Reason for control Following the Defense-in-Depth strategy introduced in Section 3. implementation and operational phases would show proper categorization of safety-critical security equipment and the proper definition of the electronic security perimeters around each of the safety related zones (SCSZ and FLSZ).1 Electronic security perimeters around SCSZ and FLSZ Ref # Version Aud. the physical intrusion detectors and alarms informing of a physical breach into a SCSZ perimeter. electronic sabotaging of a vital signaling system could cause a train collision). For example fire alarms. y FLSZ: A system whose primary function is to warn. of this equipment could lead to a threat of life safety if an emergency were to occur. When TITLE: Electronic security perimeters around SCSZ and FLSZ A 1.
4.2.2 Connecting security zones of different security levels
Ref # Version Aud. When TITLE: Connecting security zones of different security levels
B 1.0 TA Now
Reference: SP 800-53 CONTROL: All network-routable interfaces connecting the SCSZ
Primary: or FLSZ with a less-critical security zone should use an isolation
device (defined below) to ensure security separation.
The Defense-in-Depth strategy used in this Recommended Practice requires routable (TCP/IP based) network
connections to have a device to allow authorized traffic and to prohibit unauthorized traffic between the SCSZ
and FLSZ and other less-critical zones.
An isolation device may be a hardware-based firewall to filter traffic at TCP/IP stack layers 2, 3 and 4
(corresponding to link layer, IP layer and TCP layer).If technology is available, filtering at the Application
Layer is also desirable (see Appendix B for more information)
y Unauthorized network traffic is recognized and stopped at the Isolation Device
y Acceptable:
• Hardware-based firewall as described above.
y Not acceptable:
• Using a dual-homed personal computer to connect to a SCSZ or FLSZ network and also a
lesser security zone.
© 2012 American Public Transportation Association 32
4.2.3 Physical separation for SCSZ data transmission
Ref # Version Aud. When TITLE: Separation for SCSZ data transmission over optical fiber or
C 1.0 TA Now
Reference: SP 800-53 CONTROL: Separate fiber-optic strands or other acceptable
Primary: isolation methods per control 4.2.3 should be required to connect
physical separate SCSZ zones when using wide area networks
(WANs) or local area networks (LANs).
There is a need to segregate safety-critical data as it travels between SCSZs separated by distance (for
instance, from train stations to signal bungalows). Separation as described below should be provided.
This security control applies to optical fiber communication and where applicable below to copper wiring.
There are at least two techniques to provide separation for WANs and LANs connecting physically separate
WANs and LANs:
y Use a separate fiber or copper conductor for safety-critical security data.
y Use an equivalent optical technology that provides separation of data streams within the optical
medium by use of different frequencies of light, as in wave-division multiplexing (WDM) or dense
wave division multiplexing (DWDM).
y If the transit agency agrees, using a shared fiber or copper conductor for SCSZ data is permissible
provided data integrity and authenticity is protected using cryptographic means (for instance using
IPSec or similar protocols to protect the SCSZ data before blending with less critical OCSZ data )
y Note: In Part 3, separation using other techniques, such as VLANs or MPLS, will be
examined with the aid of attack modeling, and conclusions drawn as to their acceptability.
y Audit during design and implementation stages.
• Separate fiber optic strand, or copper conductor.
• optical technology providing equivalent data separation as described above
• Cryptographic protection of SCSZ data on fiber or copper medium as described above
• (See note in Discussion section above)
• Use of a dual-homed personal computer to bridge networks
© 2012 American Public Transportation Association 33
Table 13 gives security controls applicable within the SCSZ and FLSZ Electronic Security Perimeters. Each
control then has a dedicated page following the Table.
Before implementing any cyber security controls, a thorough analysis must be performed to ensure that the
controls cannot adversely impact functions implemented in the SCSZ or FLSZ.
Applies Citations (NIST NIST SP 800
Ref. Description to
to SP 800-53 Family
1 Transit A senior executive should be identified to be CA-6 Security Now
responsible and accountable for all control and Assessment and
communications security activities. Authorization
2 Transit Create a training program for employees, AT-1 Awareness and Now
vendors and partners around control and Training
3 Transit Have methods and procedures in place to create, PS-4 Personnel Security Now
modify and remove access to SCSZs and FLSZs
for people (employees, contractors, vendors and
inspectors) as their role in the organization
changes, including hire/fire or contract awarded/
expired/terminated.
4 Transit SCSZ and FLSZ electronic equipment should be PE-1 PE-2; Physical and Now
housed in a six-wall physical enclosure with two- PE-3; Environmental
factor authentication to access and warn on PE-6 Protection
5 Transit Centralized or distributed configuration CM-1 CM-2 Configuration Now
management system, manual or software based, Management
should be used for software, executables and
configuration files for each SCSZ and FLSZ
6 Transit A process should exist to manage the changes to CM-3 CM-8; Configuration Now
all SCSZ and FLSZ hardware and software with CM-9 Management
logs of the changes, including the
purpose/rationale for the changes.
7 Transit Procurement documents to specify default SA-1 SA-4 System and Now
hardening specification for SCSZ and FLSZ Services Acquisition
equipment, closing non-essential ports and
8 Transit Block any unneeded USB, CD and other entry SI-3 CM-7 System and Now
ports on SCSZ and FLSZ devices and Information
equipment. Single-factor cyber authentication Integrity;
should be used on permitted ports. Configuration
© 2012 American Public Transportation Association 34
AU-6. Information Integrity 10 Transit Bimonthly check of SCSZ and FLSZ computers. Now authorized staff should be required to change Maintenance software or executables on SCSZ and FLSZ equipment. 16 Both Method to collect and audit logs to meet the AU-1 AU-2. (to be developed) AU-4. and SP 800. 13 Both A comprehensive patch management program SI-2 System and Now should be set up with vendors for SCSZ and Information Integrity FLSZ commercial off-the-shelf (COTS) or proprietary software and firmware 14 Both Yearly passive vulnerability check should be Now performed by an authorized and qualified outside agency. Management 11 Transit Use antivirus protection or software white-listing/ SI-3 SC. System and Communications Protection 12 Transit The cybersecurity process should ensure that the CP-4 Contingency Now backup/alternate OCC cannot be used as a route Planning for sabotage or covert monitoring of activities. Integrity. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones TABLE 13 Controls References and When Applies Citations (NIST NIST SP 800 Ref. AU-12 CM-5 Audit and Now network devices and other devices that use Accountability. Description to to SP 800-53 Family Apply Appendix F) 9 Transit Bimonthly sweep for rogue wired or wireless AC-18 SI-4 Access Control. AU-5. System and Now file integrity checker on fixed/portable/mobile 7(9) Information PCs that connect to SCSZ and FLSZ equipment. AU-3. Accountability Dev 82. software for software that is unauthorized or Configuration questionable. Now devices attached to SCSZ and FLSZ System and control/communications networks. 18 Vendor Wireless communications security (to be SC-5 AC-18 System and To Be developed) Communications Dev Protection. Access Control © 2012 American Public Transportation Association 35 . 15 Both On-site physical presence by qualified and AC-17 MA-4 Access Control. AU-7 17 Vendor A vendor manager should be identified to be CA-6 Security Now responsible and accountable for all control and Assessment and communications security activities for each Authorization SCSZ and FLSZ product used by transit. Audit and To Be requirements of NIST SP 800-53.
(to be developed) 20 Vendor Use host file integrity verification with SI-7 System and To Be cryptographic checksum on SCSZ and FLSZ Information Integrity Dev controllers such as vital PLCs. “Black box” to indicate all electronic accesses and changes. Description to to SP 800-53 Family Apply Appendix F) 19 Vendor A tamper-resistant/evident “black box” should be AU-9 Audit and To Be installed locally or at a distance for SCSZ Accountability Dev controllers such as vital PLCs for forensic uses. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones TABLE 13 Controls References and When Applies Citations (NIST NIST SP 800 Ref. where not precluded by large or complex file structures. (to be developed) © 2012 American Public Transportation Association 36 .
When TITLE: Management responsibility 1 1.3. Measures of effectiveness y A job description exists that defines this responsibility for a senior executive. PM-10 security activities. The senior executive is encouraged to establish a continuous monitoring process so that changes to the system can be evaluated simply while still confirming the entire system as secure. CA-7. Discussion The senior executive is the official management person who authorizes operation of the SCSZ and FLSZ systems and explicitly accepts the risk to the organizational operations and assets. Security is more likely to be taken seriously when a senior executive is responsible and accountable in measureable ways that impact his or her job review and compensation. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. Reason for control Security needs to have visibility to be successful. y The board of directors or similar body has charged the executive team with ensuring that control and communications security is a key part of their mission.1 Management responsibility Ref # Version Aud. PM-9. Examples y Acceptable: • Written documentation that defines senior executive responsibility and accountability for control and communication security activities y Not acceptable: • No formal documentation describing the above © 2012 American Public Transportation Association 37 . The authorizing officials are in management positions with a level of authority commensurate with understanding and accepting such SCSZ and FLSZ system security risks. individuals and other organizations on the implementation of an agreed-upon set of security controls.0 TA Now Reference: SP 800-53 CONTROL: A senior executive should be identified to be Primary:CA-6 responsible and accountable for all control and communications CA-2. with a feedback mechanism that helps evaluate satisfactory performance.
Measures of effectiveness y A training program exists that covers control and communications security for personnel who operate SCSZ and FLSZ equipment and/or physically access the SCSZ or FLSZ. The training program is for all employees. When TITLE: Training program 2 1. y Not acceptable: • Simply giving personnel a training packet and requesting that they read it.2 Training program Ref # Version Aud. For example.3. with testing for retention. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. if possible. PM-9 Reason for control Control and communications security is most effective when everyone is included and made aware of the threats. A training program must touch everyone in an appropriate manner to keep everyone vigilant. just in time for an activity that is about to take place. with no follow-up. contractors and vendors who either work on-site. Discussion Control and communications security awareness and training procedures should be developed for the transit control and communications security program in general and for the SCSZ and FLSZ in particular.0 TA Now Reference: SP 800-53 CONTROL: Create a training program for employees. or remotely access transit agency systems or devices. retrain a person about password quality when he or she is about to change passwords. vendors Primary:AT-1 and partners around control and communications security. © 2012 American Public Transportation Association 38 . y Training is delivered as needed. Examples y Acceptable: • Instructor-led or computer-based training at appropriate intervals. The training is mandatory.
Clear roles of responsibility need to be established. personnel 3 1. Primary:PS-4 modify and remove access to SCSZs and FLSZs for people (employees. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. contractors. and inspectors) as their role in the organization changes. vendors. Attention should be paid to the end of contracts and to termination of employees to ensure that access is removed immediately. Examples y Acceptable: • Written procedures describing the access control system process y Not acceptable: • Informal or no procedures for access control as described above © 2012 American Public Transportation Association 39 . and access should be given only to those with a direct need for it.3. including hire/fire or contract awarded/expired/terminated. and that access is removed when no longer needed. When TITLE: Access control.3 Access Control. When a person’s responsibilities are changed (job change.0 TA Now Reference: SP 800-53 CONTROL: Have methods and procedures in place to create. Measures of effectiveness y An employee and contractor start/stop process is in place y Each person’s roles and responsibilities are defined to provide access to the appropriate software and physical areas. y A similar process exists for the start and end of contractual relationships. y An internal service level exists that these changes must be made within a very short timeframe of the person being terminated for cause or put on leave. Discussion People need access to those systems that they are directly responsible for. Reason for control There is a need to ensure that only authorized people have access to systems they require for their jobs. duty change) he or she needs to have the former access removed and the new access added. Personnel Ref # Version Aud. promotion.
something they have (e. • Secure room must comply with all applicable building codes to ensure the safety of personnel. y Not acceptable: • Simply posting a “Do not Enter” sign on an unlocked door © 2012 American Public Transportation Association 40 . a locked equipment cage that has six sides. password/passcode).. Reason for control This control is intended to ensure that the physical access to safety-critical systems is restricted to those with proper authorization. floor and ceiling secured.g. When TITLE: Access Control –Equipment 4 1.3.g.. It is not the same as using the same access control method two times in a row (such as using the same key to open an outer and an inner door. A six-wall enclosure means that there is security from all four sides. biometrics. and the bottom. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4.0 TA Now Reference: SP 800-53 CONTROL: SCSZ and FLSZ electronic equipment should be Primary:PE-1 housed in six-wall physical enclosure with two-factor PM-9 authentication to access and warn on unauthorized physical access. Measures of effectiveness y Security audit Examples y Acceptable: • Locked room with all entrances. fingerprints.4 Access Control.Equipment Ref # Version Aud.. Discussion Two-factor authentication is an acceptable means of identity assurance in high-security situations that require personnel to provide two of three factors: something they know (e. and retina). RFID badge) or something they are (e.g. the top.
there needs to be a method or process where the transit agency ensures that the compatible software versions are installed and running on all SCSZ and FLSZ devices. © 2012 American Public Transportation Association 41 . Second. incompatibilities and reasons. CM-2 PM-9 executables and configuration files for each SCSZ and FLSZ device. Reason for control A transit agency needs to know the versions of software that are currently running and whether they are up-to- date. such as naming files “File1. When TITLE: Configuration management 5 1. unaltered software and configuration settings are verified as being in-place in the field during an audit. and how they are reviewed. controlled and ultimately installed in field equipment. SCSZ filenames without a naming convention that positively identifies them.3. showing compatibilities. Third. Discussion First. y An auditor can see a diagram that explains where software and firmware originate.0 TA Now Reference: SP 800-53 CONTROL: Centralized or distributed configuration management Primary:CM-1 system. y There are controls in place to ensure that the authorized. during which time periods the software was at risk. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. and if they are not. there needs to be a way to identify the version(s) of software and firmware that work together (and are tested together) to provide safe operation. Measures of effectiveness y An auditor can see a master list of all software and firmware authorized for any time period.5 Configuration management Ref # Version Aud. should be used for software. manual or software based. there needs to be a way to distribute and monitor the software configurations throughout the safety- critical security zones of the transit system.” etc. Examples y Acceptable: • Written procedures describing a configuration management system y Not acceptable: • Ad hoc handwritten lists of software compatibilities. An audit would reveal if the versions are up-to-date.
Examples y Acceptable: • A documented change management procedure y Not acceptable: © 2012 American Public Transportation Association 42 . A typical change management process has a change approval process and a chain of custody. justification implementation. It is simply not acceptable to put a patch into the field before knowing that a safety-critical system will continue to function as required. Configuration change control includes changes to components of the SCSZ and FLSZ system. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. operating systems. When TITLE: Configuration management. it would be nearly impossible to manage the changes in a coherent and safe manner without a proven process. routers.0 TA Now Reference: SP 800-53 CONTROL: A process should exist to manage the changes to all Primary:CM-3 SCSZ and FLSZ hardware and software with logs of the changes. Configuration management helps to update hardware and software across changes in a controlled and coordinated manner. applications. CM-8 CM-9 including the purpose/rationale for the changes. test and evaluation of upgrades. It is important that logs exist to document what was done and any important equipment history along with it. audit trail Ref # Version Aud.6 Configuration management. y An audit can quickly identify when the software on any network device is the approved level. and its control and communication paths. Measures of effectiveness y An audit can determine when the system had all proper versions of software working together.3. y An audit can quickly identify when a network device’s software is not the approved level. emergency changes. and modifications before putting them into effect in SCSZ or FLSZ systems. audit trail 6 1. firewalls. such as why the change was made and who authorized it.. wireless devices and HMI).g. and changes to remediate flaws. CM-1 CM-4 CM-5 CM-6 SI-2 Reason for control In complex systems. Discussion The configuration management process should coordinate the proposal. changes to the configuration settings for software and hardware products (e.
TA purchasing needs a procurement process that includes language that will ensure that. 2009) may be used as a reference. because unnecessary services will not be accidentally overlooked or not maintained. The intent is to reduce the ways that a device or system may be compromised on purpose or by accident. When TITLE: Security in procurement 7 1. Examples y Acceptable: • Adding a procurement security specification to RFP and Purchase agreements y Not acceptable: • Leaving unnecessary ports and services activated as a default configuration. Proper procurement may also reduce the risks associated in configuration and patch management. or y if providing hardened equipment is not possible in certain instances. provide detailed documentation and procedures to perform it. DHS’s “Cyber Security Procurement Language for Control Systems” as revised (Revision 4. © 2012 American Public Transportation Association 43 . including the closing of non-essential ports and services. closing non- PM-9 essential ports and services. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. Reason for control SCSZ and FLSZ control and communications equipment is best delivered from the vendor with security pre- configured in at delivery time. Discussion Transit agency procurement documents should include requirements for vendors to: y supply SCSZ and FLSZ equipment hardened. Measures of effectiveness y Audit of “as-received” SCSZ and FLSZ equipment.3. October 8.7 Security in procurement Ref # Version Aud.0 TA Now Reference: SP 800-53 CONTROL: Procurement documents to specify default hardening Primary:SA-1 SA-4 specification for SCSZ and FLSZ equipment.
any connection attempt leads to a one-factor authentication. CD and other entry ports Primary:SI-3 CM-7 on SCSZ and FLSZ devices and equipment. the person connecting the device should be required to authenticate to the system to authorize the connection. y When a port is active. In the case where a device must legitimately be connected. network devices and computers. SI-1 SI-4 SI-7 Reason for control A transit agency needs to prevent unauthorized connections to SCSZ equipment. due consideration should be placed into device control mechanisms. When TITLE: Physical security. y Logical means are used to disable legitimate connection points without proper authentication. Attachments Ref # Version Aud. mobile access control mechanisms and device encryption. Discussion Security attacks are often done by connecting an infected device to a secure device or network. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. attachments 8 1.0 TA Now Reference: SP 800-53 CONTROL: Block any unneeded USB. Measures of effectiveness y Devices or physical protections are used to block unused ports and connectors in routers. switches. CDs and other devices in the hope that an unsuspecting person will connect them to the systems. it should insist on some single-factor type of authentication (such as a password) before accepting the connection. If someone does connect an authorized device to the system. In cases where mobile media is necessary for proper operations.8 Physical Security. To prevent the attachment of unauthorized devices. Single-factor cyber SA-4 SA-8 SA-12 SA-13 authentication should be used on permitted ports. you should eliminate the ability to attach the device if that port is unneeded.3. Attackers infect removable media such as USB drives. Other attack methods include connecting unauthorized devices to the systems or network. Examples y Acceptable: • Unneeded ports are blocked y Not acceptable: • © 2012 American Public Transportation Association 44 .
0 TA Now Reference: SP 800-53 CONTROL: Bimonthly sweep for rogue wired or wireless devices Primary:AC-18 SI-4 attached to SCSZ and FLSZ control/communications networks. detection 9 1. but also ensures that access points to your network are not bypassing access-control mechanisms put in place to protect the system. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. Devices are so small and can be powered by battery. so it may be very difficult to find a device that is eavesdropping on your wireless telecommunications. It should do this by regularly analyzing the network for such devices. A bimonthly scan of the network for detection of rogue devices not only prevents changes to the system that have not been authorized or tested. Examples y Acceptable: • Check for unauthorized devices done considering possible negative responses of the control network to the scan or sweep method used y Not acceptable: © 2012 American Public Transportation Association 45 . They also want to detect and remove devices that may masquerade as legitimate devices and may take control of part or their entire network. AC-3 AC-18 IA-2 IA-3 IA-8 SI-4 Reason for control A transit agency needs to know if an unauthorized device is eavesdropping or intruding on its network.3. Discussion Transit agencies want to prevent unauthorized collection of information from their systems. Rogue devices may also be connected directly to your network.9 Unauthorized devices. Caution: The method used to scan or sweep the network must be proven not to have negative an operational impact on the system. Measures of effectiveness y There is a scheduled review of devices connected to the network. y The transit agency has a definition of what an authorized device is. detection Ref # Version Aud. When TITLE: Unauthorized devices.
vetted through testing. The configuration management system should contain a master list of software that is approved and the version that should be run. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. compliance 10 1. and other devices that use software for CM-5 software that is unauthorized or questionable. © 2012 American Public Transportation Association 46 . and determined safe for use could cause negative impacts to the system and may actually be or contain malicious software.10 Unauthorized Software. y The checks identify unapproved software. When TITLE: Unauthorized software. then monitor and alert on unauthorized software present or config changes y Not acceptable: • No software check performed. Software that has not been identified. and an action plan is in place to: y determine if the found software should be added to the approved list. Examples y Acceptable: • Any scans used to check for unauthorized software should be compatible with the control system being scanned. based upon job function. and y find a way to mitigate the software in question. A scan may also check for known but unacceptable software. y remove software found to be unauthorized. Any changes to the software on a system should be authorized per the configuration management and change control process. • Use of a software audit configuration tool to establish a software baseline. It is therefore recommended that personnel perform bimonthly checks of the system to verify that the system meets expectations. Primary:AU-12 network devices.0 TA Now Reference: SP 800-53 CONTROL: Bimonthly check of SCSZ and FLSZ computers. will show when there may be a risk.3. A period comparison of which software is available to each person. Reason for control There is a wide array of software needed to run each aspect of a transit agency. Compliance Ref # Version Aud. Discussion This control is intended to ensure proper configuration management of systems with approved software. such as remove it to a less-sensitive portion of the network. Measures of effectiveness y Audit.
Malicious code can also be encoded in various formats (e. y Have a process to ensure that any equipment being brought into SCSZ and FLSZ areas is free and clear of malicious code. When TITLE: Active malware protection 11 1. SA-12 SA-13 SI-1 SI-4 Reason for control Cyber-attacks often start with entry via a PC or laptop. Examples y Acceptable: • Antivirus software with updating process for signature database. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. The transit agency needs an active monitoring and reporting solution. CM-1 CM-5 integrity checker on fixed/portable/mobile PC's that connect to SA-1 SA-4 SA-8 SCSZ and FLSZ equipment. white-listing/file integrity check software to detect malware or file modification. y Not acceptable: • No malware protection © 2012 American Public Transportation Association 47 .g.11 Active malware protection Ref # Version Aud. UUENCODE.0 TA Now Reference: SP 800-53 CONTROL: Use antivirus protection or software white-listing/ file Primary:SI-3 SC-7(9).. A variety of technologies and methods exist to limit or eliminate the effects of malicious code attacks. adware. spyware and similar malicious code should be actively protected via real-time monitoring products. The malicious code may be introduced via the web. removable media such as a thumb drive or through rogue software installed as part of the code provided. Measures of effectiveness y Identify the operating systems that must be actively monitored. that it is active and that a recent scan has shown the PC or laptop to be free from infection. Pervasive configuration management and strong software integrity controls may be effective in preventing execution of unauthorized code. Transit agencies should have a process to ensure that any equipment entering their facilities has up-to-date scanning software. Discussion Commercial off the shelf operating systems that are vulnerable to computer viruses.3. Unicode) or contained within a compressed file.
it is not fully staffed. Measures of effectiveness y The backup or alternate OCC is always included in all testing and vulnerability assessments. y The backup or alternate OCC and its telecommunications systems are routinely updated to match the primary OCC. a fully operational center. Examples y Acceptable: y Not acceptable: © 2012 American Public Transportation Association 48 . Discussion The transit agency needs to test and/or exercise contingency plans to identify potential weaknesses. the transit agency must actively monitor it for suspicious activities.3. Reason for control The backup/alternate OCC is. and this makes it a target for saboteurs to plant monitoring devices. When TITLE: Operations control center. or plans exist to bridge the differences. There may be unexpected communication paths between the primary and alternate OCCs.0 TA Now Reference: SP 800-53 CONTROL: The cybersecurity process should ensure that the Primary:CP-4 backup/alternate OCC cannot be used as a route for sabotage or CP-1 covert monitoring of activities. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. alternate 12 1. However. The disaster recovery plans and business continuity plans should explore the vulnerabilities that can exist when the alternate OCC is only partially operational through being fully operational. In addition to keeping the alternate OCC either partially or fully operational. It also makes an ideal place to inject malicious code.12 Operations Control Center. Alternate Ref # Version Aud. in theory and often in practice.
Discussion SCSZ and FLSZ systems have various components. When TITLE: Patch management 13 1. y Whether a patch affects this system (many patches are for features not used). APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4.3. SI-1 SI-11 Reason for control Firmware and software need to be modified for both functionality and vulnerability. yet occur within a reasonable period of time. For instance. some which should be updated only in a coordinated manner with their associated control system. operating schedules and assurance of adequate patch testing offline before patches are installed. Certified vendor patches should be supplied for both proprietary and Commercial off the Shelf firmware and software that is part of the Vendor’s supplied equipment. configuration management software compatibility lists should be consulted to ensure that patching one piece of software doesn’t adversely affect correct operation of another. The decision about when the transit agency applies the patch should be made by the transit agency based on criticality. and regression testing. Vendors of SCSZ and FLSZ software and firmware should work with ICS-CERT on any discovered vulnerability. the ICS-CERT database run by the Department of Homeland Security records and tracks vulnerability and patch update information. may be updated based upon the software vendor’s recommendation. Note: Guidance for setting up a patch management program may be found in the DHS CSSP “Recommended Practice for Patch Management of Control Systems”. or a buffer overflow allowing remote administrative privileges. For control systems. often the HMI. Other components. Measures of effectiveness y A patch management program exists for each vendor’s SCSZ and FLSZ products.0 BOTH Now Reference: SP 800-53 CONTROL: A comprehensive patch management program should Primary:SI-2 be set up with vendors for SCSZ and FLSZ commercial off the CA-2 CA-7 CM-3 MA-2 IR-4 RA-5 SA-11 shelf (COTS) or proprietary software and firmware. would be judged to be more serious than a difficult to exploit denial-of-service attack. Care must be taken to test the updates before applying them in the field. and the potential consequences that an exploit of this vulnerability would have on field equipment. Additionally. y An assessment process exists for the risk of not applying a patch: y Whether a system is completely and truly isolated (very rare). the discovery of a remotely exploitable shell with an easy-to-deduce or default password. December 2008 (see references) The time schedule agreed upon for supplying a patch should allow enough time for thorough vendor evaluation of the vulnerability.13 Patch management Ref # Version Aud. The transit agency must coordinate with the vendor so that updates can be applied without compromising safety and security. © 2012 American Public Transportation Association 49 . The speed and nature of the response to the vulnerability should depend on the severity of the vulnerability. HMI or the underlying operating system with the hardware vendor or integrator’s approval.
© 2012 American Public Transportation Association 50 . Examples y Acceptable: • Vendors working with ICS-CERT and transit agencies on a documented patch management program y Not acceptable: • No patch management program exists. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones y What other co-requisites are needed to install this patch.
© 2012 American Public Transportation Association 51 . Reason for control A transit agency should have an outside agency assess. Measures of effectiveness y A contract exists for this activity.3. The transit agency should have baselines and configuration management monitoring systems that ensure that the entire system is operationally correct and the least vulnerable to cyber-attack as can be done reasonably. its vulnerability to cyber-attack in the SCSZ and FLSZ. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. validation 14 1.0 VEND Now Reference: SP 800-53 CONTROL: A yearly passive vulnerability check should be Primary: performed by an outside authorized and qualified agency. at least annually. When TITLE: Security compliance. The senior executive of the transit agency should signoff on the results of the assessment and put mitigations in place as necessary to keep the transit system safe and secure.14 Security compliance. The vulnerability assessment is to use control and communications security criteria current at the time of the assessment. Discussion The assessment is to ensure that the continuous improvement processes are addressing the needs to keep the transit system cyber secure. Examples y Acceptable: • Using an outside agency with experience and qualifications on testing control systems y Not acceptable: • Active vulnerability scans used on IT-type network equipment. which may affect control and communications equipment adversely. validation Ref # Version Aud.
3. This may be accomplished by using two-factor authentication to access the physical space where the device is located. y Not acceptable: • Remote change of safety-critical executable files from a distance using a web interface or telephone modem. safety-critical equipment Ref # Version Aud.15 Access Control. © 2012 American Public Transportation Association 52 . When TITLE: Access Control. Measures of effectiveness y Audit Examples y Acceptable: • On-site physical presence. it should be done in-person. Restricting both physical and electronic access is important to safety and security. followed by at least single-factor cyber authentication to modify the SCSZ equipment. Discussion Whenever a SCSZ or FLSZ device is being accessed. safety-critical equipment 15 1. IA-3 IA-8 Reason for control Safety-critical equipment needs to be protected to a greater extent than other equipment. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4.0 BOTH Now Reference: SP 800-53 CONTROL: On-site physical presence by qualified and authorized Primary:AC-17 MA-4 staff should be required to change software or executables on AC-3 AC-18 AC-20 IA-2 SCSZ and FLSZ equipment.
0 TA To Be Dev Reference: SP 800-53 CONTROL: Method to collect and audit logs to meet the Primary:AU-1 AU-2 AU-3 requirements of NIST SP 800-53 and SP 800-82. (to be developed) AU-4 AU-5 AU-6 AU-7 PM-9 Reason for control Audit logs provide accountability and forensic information. The audit and accountability policy should be included as part of the general control and communication security policy for the organization. When TITLE: Audit and accountability. Their collection helps determine when cybersecurity was in place and when an issue was present. Examples y Acceptable: y Not acceptable: © 2012 American Public Transportation Association 53 . y The transit agency has a process to align the information from different logging systems to track across its system events that substantially occurred at the same time. Logs should be analyzed regularly to reveal unexpected conditions. The challenge is the time difference (albeit slight) across disparate systems.3. Measures of effectiveness y An audit shows which devices have audit logs and have configured the logging to the level necessary for an audit without disrupting operations. In a finely tuned system. one can determine exactly the order of changes and events across systems. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. which should be addressed by retraining. logs Ref # Version Aud. Logs 16 1.16 Audit and Accountability. Discussion Audit logs are used to determine if there are anomalies or repeated bad behaviors by users.
Vendors with no cybersecurity knowledge base on their products. Measures of effectiveness y Transit agency customer satisfaction. The vendor can have many people involved in this process. each relevant device and product should have at least one cybersecurity point of contact. products and architecture are secure. vendor product management 17 1. y Not acceptable: • “Just-in-time” or “ad hoc” researching of control and communications security questions and problems from transit agencies. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. When TITLE: Responsibility. however. © 2012 American Public Transportation Association 54 . Reason for control Transit agencies need to know whom to contact at a vendor to answer control and communications security questions about a vendor’s products.3. Discussion Each transit agency needs to have a single point of contact at each vendor who is knowledgeable about the cybersecurity aspects of SCSZ devices used by the transit agency.0 VEND Now Reference: SP 800-53 CONTROL: A vendor manager should be identified to be Primary:CA-6 responsible and accountable for all control and communications CA-2 CA-7 PM-9 PM-10 security activities for each SCSZ and FLSZ product used by transit. The vendor needs to have someone responsible for keeping up-to-date on cybersecurity issues and for ensuring that its devices. vendor product management Ref # Version Aud. leading to search of a vendor organization for cybersecurity knowledgeable people. Examples y Acceptable: • Control and communications security knowledgeable experts at vendor customer service locations who know both the equipment in question and cyber security.17 Responsibility.
it must be replaced. wireless security Ref # Version Aud. If any equipment uses a now-compromised protocol. Examples y Acceptable: y Not acceptable: © 2012 American Public Transportation Association 55 . (e. y unauthorized access. The purpose is to prevent: y revealing operational data to snoopers.11 Wi-Fi–acceptable protocols being unacceptable tomorrow. and y unauthorized tampering with information being sent to the OCC or to another system. The agency should determine which protocols are appropriate and use only those. Discussion This control is intended to protect wireless communications with acceptable protocols that provide authentication and encryption.3. Wireless communications that have direct access to a safety- critical system must also be highly protected. which itself uses encryption. Other communications protocols that are available should be investigated to ensure that the procurement includes requirements to meet acceptable encryption guidelines and are capable of performing mutual authentication to ensure that the devices/users are authorized to connect to the system wirelessly. Measures of effectiveness y VPN definition exists.0 VEND To Be Dev Reference: SP 800-53 CONTROL: Wireless communications security (to be developed) Primary:SC-5 AC-18 SC-1 AC-1 Reason for control Safety-critical systems must be highly protected.g. When TITLE: Wireless security 18 1. There is a history of today’s IEEE 802.. y The intervening communication “pipes” are also protected from Man-in-the-Middle attacks. The best protection available today is a VPN.18 Communications. Wired Equivalent Privacy [WEP]). especially sending commands to the critical system. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4.
0 VEND To Be Dev Reference: SP 800-53 CONTROL: A tamper-resistant/evident “black box” should be Primary:AU-9 AC-3 installed locally or at a distance for SCSZ controllers such as AC-6 vital PLCs for forensic uses. regardless of environmental problems or attempts to tamper with critical equipment. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4. audit trail Ref # Version Aud. “Black box” to indicate all electronic accesses and changes. audit trail 19 1. When TITLE: Forensic device for SCSZ controller. (to be developed) Reason for control Transit agencies need a way to know what happened in every situation.19 Forensic device for SCSZ controller. especially if that equipment cannot log and save an audit trail of changes made to it. especially to determine if a violation or corruption occurred. Measures of effectiveness Examples y Acceptable: y Not acceptable: © 2012 American Public Transportation Association 56 . The information will be/may be used to confirm changes made to the PLC. Discussion This control is intended to provide an audit trail and recording of all changes made to vital PLCs and related equipment that do not usually have their own logging ability.3.
One way to do this is by comparing cryptographic checksums with the checksums stored in a configuration-managed database. Discussion Each PLC and controller should have a known configuration of software and firmware. y Not acceptable: • Using only CRC or similar checksums to verify file integrity. Comparing the PLC or controller’s software and firmware to a controlled version that has not and cannot have been tampered with ensures that the operational PLC or controller also has not been tampered with. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 4.0 VEND To Be Dev Reference: SP 800-53 CONTROL: Use host file integrity verification with cryptographic Primary:SI-7 checksum on SCSZ and FLSZ controllers such as vital PLCs.3. The testing order should not be predictive so that a malicious actor cannot exploit the window between tests. When TITLE: Validate PLC and controller integrity 20 1. The transit agency should be able to confirm that files on each SCSZ PLC or controller have not been tampered with. and a non-cryptographic checksum may be spoofed. Measures of effectiveness y There is a master copy of PLC and controller firmware and software saved in a disconnected and protected method for each unique configuration of PLC and controller. y A process exists to perform this test for every PLC and controller periodically. Transit agencies need to detect tampering.20 Validate PLC and controller integrity Ref # Version Aud. (to be developed) Reason for control It is important to know that the software/firmware that a PLC or controller is running is the approved. Examples y Acceptable: • Using a current NIST-approved cryptographic checksum such as SHA-2. SI-1 where not precluded by large or complex file structures. © 2012 American Public Transportation Association 57 . tested and validated software and firmware.
FIGURE 9 Safety-Critical Testing 5.2) are protecting the routable network connections. Note that the network connections are consistent with Figure 8. Note also that the firewalls (isolation devices. life-safety LANs in the OCC and the train stations. Applying security controls to zones 5. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 5. Note the electronic security perimeter around the fire.2.2. © 2012 American Public Transportation Association 58 .2). per Section 4.2 Safety-critical Fire Life Safety Figure 10 illustrates the application of Part II security controls to a generic FLSZ. per Section 4.1 Safety-critical signaling Figure 9 illustrates the application of SCSZ requirements to a generic signaling bungalow using a block signaling approach. and that they are both protected with firewalls (isolation devices.
The cyber-protection requirements for this zone are generally less strict than the protection for the SCSZ or the FLSZ. but excludes the safety-critical and fire-life safety systems in the SCSZ and FLSZ. however.2 and 3. The main topics will be the following: y Protecting the OCSZ y Securing the train line control and communications systems y Applying attack modeling for rail transit control and communications systems 6. such as zone isolation and protection. ATS. such as dispatch. need control and communications security measures. Part III Section 1. this includes systems in the control room and train stations.2 gives the breakdown of the three parts of the APTA Recommended Practice series “Securing Control and Communications Systems in Transit Environments. Preview of the Recommended Practice series. The zone does. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones FIGURE 10 Safety-Critical Fire Life Zone 6.7.” This section gives a preview of topics that will be covered in Part III of the series. SCADA.3. the OCSZ covers systems needed to run and maintain normal revenue operations. Referring to Figure 6.7. traction-power SCADA. © 2012 American Public Transportation Association 59 . etc. These systems need cyber-protection. A failure of these systems normally results in stopped trains or a non-operational railway.1 Protecting the OCSZ Per Sections 3.
2 Securing the train line control and communications Train-sets are becoming more networked. which would be an input to the security zone classification process. For instance. over-speed control and ATP. y Describe normal and intermittent sequence of operations of the system. passenger door control. and Availability (CIA). operational and maintenance data streams. diagnostic and maintenance data. y Operational systems and networks. The APTA attack-modeling procedure will be described in Part III. such as for video-feeds.3 Attack modeling for transit control and communications systems Attack modeling is a relatively new discipline within the area of control system security. along with data flow diagrams (DFD). Integrity. y Decompose operations into sequence diagrams. There are a variety of methods to do attack modeling today. including vital systems such as brakes. accidental error). The following classes of systems are identified as a minimum set. acceleration. which would include vital. to supply connectivity for passenger laptops and personal communications devices. y Describe and rate the risks. Confidentiality. It is not known in advance how the above systems will be segmented into security zones in Part III. outsider. © 2012 American Public Transportation Association 60 . It was popularized as a necessary step in Microsoft’s 2006 manual for its Software Development Life Cycle (SDLC) under the name “Threat Modeling”. y Analyze vulnerabilities. y Identify the range of attacks (insider. y Train-to-wayside communications. y Identify risk cutoff level. along with personnel protective and emergency systems. y Passenger entertainment and wireless (Wi-Fi) networks. similar to what has been done for the stationary rail assets in Part II: y Safety-critical assets. 6. computerized and automated every year. The procedure developed by APTA for rail transit attack modeling has the following steps: y Characterize the system assets and networked connections. and DREAD. and an example given. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones 6. y Build attack trees to describe and examine these attacks. emergency interlocks and shutoffs would be included. using procedures known as STRIDE.
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Appendix A: Control and communications system account worksheets The following worksheets are to guide a transit agency in placing a functional area into the appropriate security zone. © 2012 American Public Transportation Association 61 .
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Operations Control Center © 2012 American Public Transportation Association 62 .
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Train station © 2012 American Public Transportation Association 63 .
APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Signal hut © 2012 American Public Transportation Association 64 .
and detecting unauthorized software (Section 4. However.1.1 Possible Isolation Techniques You may be able to use the application layer of the Ethernet/TCP/IP (internet) stack for communication isolation. such as configuration management (Section 4.2 .2 Deep packet inspection firewalls – Depending on the protocol used. mitigating security controls may be put in effect such as: B.1.2. They are: B. design and implement.2. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Appendix B: Out-of-Scope Item Discussion This appendix gives guidance for two topics that are out-of-scope for this RP and are of interest to transit agencies and vendors: B. At the application layer.1. such as insulating these devices from external connections B. filtering at the Application Layer is also desirable” B. there may be application layer firewalls that look at every application layer packet to separate out illegal or unauthorized commands to networked equipment © 2012 American Public Transportation Association 65 .3. techniques that eliminate buffer overflow.1.3. and other coding vulnerabilities may be introduced B.1.2. Using the defense in depth model.2 .1.2.2 Security Control – How to provide isolation [Reference: Section 4.Defining a Security Zone Architecture and Protecting the Safety-Critical Zone] B.2. and require more technical knowledge to research. Some security controls affecting the application layer are listed in this document.5). develop. use of antivirus or whitelisting software (Section 4.Connecting security zones of different security levels] Additional comments on the following statement in the “Discussion” section of the security control requiring security isolation .1 A secure software plan by the vendors. format string vulnerabilities.1 Preliminary suggestions and selected references Preliminary suggestions and selected references for retrofitting security upgrades for legacy equipment presents special issues for transit agencies.1 Extra protection around the perimeter of these devices.2 Increased use of personnel or physical security measures as compensating or mitigating controls B.1.“If technology is available.1 How to Approach Security Retrofits for Legacy Systems [Reference Section: 1. there are a host of techniques that are generally more sophisticated.3.10).10).
00. August 2009. National Institute of Standards and Technology (NIST).gov/groups/SMA/fisma/ics/documents/papers/Apply-SP-800-53- ICS-final-22Aug06.pdf National Institute of Standards and Technology (NIST). Signalling and Processing Systems .gov/ia/_files/support/defenseindepth. “Security Technologies for Industrial Automation and Control Systems.01. http://csrc.Communication. and Models.” ANSI/ISA Technical Report TR99.nist. http://csrc.pdf National Institute of Standards and Technology (NIST). 2007. June 2010.00. http://www.pdf National Institute of Standards and Technology (NIST).aptastandards. “Security for Industrial Automation and Control Systems: Part 2: Integrating Security into the Manufacturing and Control Systems Environment.gov/publications/nistpubs/800-53A-rev1/sp800-53A-rev1-final.” ANSI/ISA Standard 99.pdf National Security Agency (NSA).gov/publications/nistpubs/800-82/SP800-82-final. http://csrc. “Securing Control and Communications Systems in Transit Environments.” July 2002.com/Documents/PublishedStandards/Security/tabid/329/language/en- US/Default.” February 2004. “Risk Management Guide for Information Technology Systems.pdf Also see: sp800-53-rev3-final_updated-errata_05-01-2010.pdf National Institute of Standards and Technology (NIST).” final.gov/publications/fips/fips199/FIPS-PUB-199-final. “Guide to Industrial Control Systems (ICS) Security. June 2011.pdf © 2012 American Public Transportation Association 66 .nist. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones References American Public Transportation Association Recommended Practice.” Revision 1.02. http://csrc. International Society of Automation.Safety Related Communication in Closed/Open Transmission Systems”.gov/publications/nistpubs/800-30/sp800-30.nist. “Recommended Security Controls for Federal Information Systems and Organizations.” APTA RP-CCS-1-RT-001-10.00.nist. July 2010. September 2010 Federal Information Processing Standards (FIPS) Pub 199. Terminology. “Defense in Depth: A practical strategy for achieving Information Assurance in today’s highly networked environments.” Revision 3. includes updates from May1.pdf International Society of Automation.nsa. “Security for Industrial Automation and Control Systems: Part 1: Concepts.”. “Standards for Security Categorization of Federal Information and Information Systems.01. 2010.” ANSI/ISA Standard 99. “Applying NIST SP 800-53 to Industrial Control Systems.” August 2006.gov/publications/nistpubs/800-53-Rev3/sp800-53-rev3-final. http://csrc.nist. International Society of Automation.aspx CENELEC standard EN 50159 “Railway Applications . 2007.nist. http://csrc. “Guide for Assessing the Security Controls in Federal Information Systems and Organizations. http://www. 2007.
“Recommended Practice: Improving Industrial Control Systems Cybersecurity with Defense-In-Depth Strategies.S. Department of Homeland Security National Cyber Security Division. Department of Homeland Security National Cyber Security Division “Recommended Practice for Patch Management of Control Systems”. December 2008 http://www.” October 2009.pdf U.pdf © 2012 American Public Transportation Association 67 .gov/control_systems/practices/documents/PatchManagementRecommendedPractice_Final. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones U. http://www.S.us- cert.us-cert.gov/control_systems/practices/documents/Defense_in_Depth_Oct09.
configuration management: A practice and process of handling hardware. Exploitability. emergency cutoff (blue light) system: A safety system installed at passenger stations that cuts off traction power and notifies the control center that power has been cut at this location. cyclic redundancy check (CRC): An error detection code used in digital networks to detect accidental changes in data during transmission or storage. and Discoverability. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Definitions automatic train protection (ATP): A wayside and/or on-board train system to apply emergency brakes if a signal is missed by the train operator. automatic train supervision (ATS): Provides advanced functionalities of train control. automatic train control system that relies on wayside data communications and/or GPS for position sensing and uses the “moving block” principle for safe train separation rather than fixed blocks with track circuits. © 2012 American Public Transportation Association 68 . There are many methods to encrypt and decrypt a message. DREAD: A Microsoft risk-assessment technique that categorizes a threat by evaluating it in each of five categories: Damage. a logical perimeter drawn around electronic assets in a security zone to separate it from other zones. software and firmware changes systematically so that a device or system maintains its integrity over time. fail-safe: A device that fails in a manner that protects the safety of personnel and equipment. Defense-in-Depth: A layered approach to information security that uses multiple computer security techniques to help mitigate the risk of one component of the defense being compromised or circumvented. and non-safety-critical information. cryptography: A way to encode (hide) information such that the sender intends that only the recipient should understand the message. Affected Users. It is used in the same sense of an aviation flight recorder. The highest numbers indicate the highest threats. black-box: A device that records information. which cannot be changed or manipulated in any manner. Reproducibility. The information recorded is used for forensic purposes. Some are shared such that many can decipher (decode) the message. life-safety. The sum of all of the ratings is used as the overall rating of the threat. commercial-off-the-shelf (COTS): Products that are readily available commercially and may be used “as is.” communications-based train control (CBTC): A continuous. and others are specific to a pair of entities that wish to communicate a secret. cybersecurity: The field of protecting digital computers and networks from accidental or malicious modifications. non-fire. Enterprise Zone: The zone of a transit agency that handles its routine internal business processes and other non-operational. electronic security perimeter (ESP): Adapted from NERC-CIP electric power regulations. typically including advanced automatic routing and automatic train regulation.
It may handle just one system or many systems simultaneously. including advertisements. some portion of a transportation system. The June 2011 final version was used in preparing this document. human-machine interface (HMI): The control interface between humans and machines. confidential information. emergency notification. malware: Short for malicious software. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones fiber-optic strand: A portion of a cable in a fiber-optic network. coordinated method for equipment vendors to update software and firmware fixes for their digital equipment at transit agencies in a timely and responsible manner. entitled “Guide to Industrial Control Systems (ICS) Security” (see References). Such software is created and used by people. NIST SP 800-82: NIST Special Publication 800-82. man-in-the-middle (MitM): A type of cyber-attack where an interloper inserts him. interlocking: An arrangement of railway signals and signal appliances so interconnected that their movements must succeed one another in proper sequence. Each strand carries information unique to it and is isolated from all the other strands. such as SCADA. Safety Critical Security Zone (SCSZ): The zone that contains vital signaling. without consent. August 2009. Fire Life-Safety Security Zone (FLSZ): A zone containing systems whose primary function is to warn. protect or inform in an emergency. SCADA: A control system involving a master terminal unit and remote terminal units. usually with bad intentions. time. announcements.Revision 3. without either side being aware of the interloper. passenger information display: An electronic information system that provides real-time passenger information.or herself in-between two communicating devices. was used in preparing this document. dispatch and ATS. etc. reason for the status and destination. to disrupt computer operations or obtain. Additionally. Operationally Critical Security Zone (OCSZ): A security zone containing systems necessary for proper operation of rail transit. entitled “Recommended Security Controls for Federal Information Systems and Organizations” (see References). programmable logic controller (PLC): An industrial computer used for automation of mechanical processes. © 2012 American Public Transportation Association 69 . patch management: A regular. and in some cases controls. it may display other information. interlocking and ATP within rail transit. The application of a Recommended Practice is voluntary. operations control center (OCC): A central location that monitors. such as arrival of trains and their status. It contains systems such as fire alarms and emergency ventilation. IPSec: A suite of protocols for securing Internet Protocol communications that authenticates and encrypts each IP packet in a communication session. NIST SP 800-53: NIST Special Publication 800-53. used for supervisory control and data acquisition. Recommended Practice: An APTA Recommended Practice represents a common viewpoint of those parties concerned with its provisions.
vital: A term applied within rail safety to denote fail-safe operation. vector (for cyber-attack): The path an attacker takes to attack a network.”) vital-programmable logic controller (vital-PLC): A PLC with fail-safe functions intended for safety-critical signaling and interlocking applications in rail transit. virtual local area network (VLAN): A method to connect devices. traction power: A network supplying power to electrically powered railways. all short-range communications that use some type of electromagnetic spectrum to send and/or receive information without wires.g. mobility.1Q. USB: Used to denote a device that uses USB as a communications method—e. These factors may include something the user has. The acronym stands for Spoofing of an id. © 2012 American Public Transportation Association 70 . access or recognition. it is known that the network’s integrity is intact and that no intruder is present. 2000 glossary. “vital function: A function in a safety-critical system that is required to be implemented in a fail-safe manner. (This term is borrowed from biology. trusted (network): Network of an organization that is within the organization’s ability to control or manage. It is most commonly implemented using IEEE 802. and Elevation of privilege. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Secure Hash Algorithm (SHA): A family of cryptographic hash functions used to calculate a unique sum for a digital file to be used to check for later file modifications. much as what a router would provide at Layer 3. Denial of service. services.. where disease is traced from its origin through the various carriers and paths taken to infect the victim). that communicate on a network as if they were on a separate network segment. at ISO Layer 2. Tampering with data. two-factor authentication: A method of authenticating a user whereby at least two distinct factors are verified. STRIDE: Defines a Microsoft method to classify computer security threats. vital signaling: The portion of a railway signaling network that contains vital equipment. Wi-Fi: In the broadest sense. something the user knows. such as the Internet. track circuit: An electrical circuit designed to indicate the presence or absence of a train in a specific section of track. Repudiation. Information disclosure (breach). A VPN in and of itself is not necessarily secure. thumb-drive/memory stick. virtual private network (VPN): A computer network in which some of the connections are virtual circuits instead of direct connections via physical wires within some larger network. Further. (Derived from IEEE Standard 1483. or something the user is or does. white-listing: Describes a list or register of entities that are granted certain privileges.
National Security Administration NERC North American Electric Reliability Corporation NERC-CIP North American Electric Reliability Corporation – Critical Infrastructure Protection NIST National Institute of Standards and Technology OCC operations control center OCSZ Operationally Critical Security Zone PC personal computer PLC programmable logic controller PTC positive train control RFID radio frequency identification SCADA Supervisory Control and Data Acquisition SCSZ Safety Critical Security Zone SHA-2 Secure Hash Algorithm. second version SME subject matter expert ST-ISAC Surface Transportation Information Sharing and Analysis Center TA Transit Agency TCP/IP Transmission Control Protocol/Internet Protocol TSA U. Department of Homeland Security DWDM dense wave division multiplexing ESP electronic security perimeter FIPS Federal Information Processing Standard FLSZ Fire.S. APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones Abbreviations and acronyms AES Advanced Encryption Standard APTA American Public Transportation Association ATP automatic train protection ATS automatic train supervision CBT Computer Based Training CBTC communications-based train control CCSWG Control and Communications Security Working Group CCTV closed-circuit television CD compact disc CIA Confidentiality. Transportation Security Administration USB universal serial bus © 2012 American Public Transportation Association 71 .S.S. Availability CO carbon monoxide CO2 carbon dioxide COTS commercial-off-the-shelf CRC cyclic redundancy check CSSP Control Systems Security Program DHS U. Life-Safety Security Zone FTP file-transfer protocol HMI human-machine interface ICS Industrial Control System ICS-CERT Industrial Control Systems – Computer Emergency Response Team IEEE Institute of Electrical and Electronics Engineers (commonly just IEEE) IPSec Internet Protocol Security ISA International Society of Automation IT information technology MitM man-in-the-middle NSA U. Integrity.
Volpe National Transportation Systems Center of the U.S. Department of Transportation VPN virtual private network WDM wave-division multiplexing WEP Wired Equivalent Privacy © 2012 American Public Transportation Association 72 . APTA-SS-CCS-RP-002-13 Defining a Security Zone Architecture for Rail Transit and Protecting Critical Zones VLAN virtual local area network Volpe John A.
Documents Similar To Apta Ss Ccs Rp 002 13
ISO27k Security Presentation v1.0
Divesh Jagtap
More From aqib ali
Apa Jonestown.en.de 1
holidays 2017.pdf
01 - Engineering Materials
WA 0812 985 1 4168, Feng Shui Condominium Unit, Feng Shui Kamar Tidur Suami IstriUploaded by Harga Jasa Desain Logo Arsitektur Keren
kata2 alghazaliUploaded by nadirahamnk
Kelas_08_SMP_IPS_Siswa.pdfUploaded by sheiie
Condicionamiento Uploaded by prueba prueba
w22Uploaded by Mateus Landim
Control de Inventario Alamacen TallerUploaded by SonQo Sua