Abstract:
A system for augmenting an attacker map of a network of resources, including a deception management server within a network of resources, generating an attacker map for the network, the attacker map including one or more attack paths traversing some or all of the resources, each attack path corresponding to one or more successive attack vectors, wherein an attack vector is an object in memory or storage of a first resource of the network that may potentially lead an attacker to a second resource of the network, and a deployment module for planting one or more decoy attack vectors in some of all of the resources of the network, wherein the deception management server generates an augmented attacker map by augmenting the attack paths based on the decoy attack vectors added by the deployment module.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/004,904, now U.S. Pat. No. 9,553,885, entitled SYSTEM AND METHOD FOR CREATION, DEPLOYMENT AND MANAGEMENT OF AUGMENTED ATTACKER MAP, and filed on Jan. 23, 2016 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky. U.S. patent application Ser. No. 15/004,904 is a non-provisional of U.S. Provisional Application No. 62/172,251, entitled SYSTEM AND METHOD FOR CREATION, DEPLOYMENT AND MANAGEMENT OF AUGMENTED ATTACKER MAP, and filed on Jun. 8, 2015 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky. The contents of these applications are hereby incorporated by reference herein in their entirety. 
     U.S. patent application Ser. No. 15/004,904 is a non-provisional of U.S. Provisional Application No. 62/172,253, entitled SYSTEM AND METHOD FOR MULTI-LEVEL DECEPTION MANAGEMENT AND DECEPTION SYSTEM FOR MALICIOUS ACTIONS IN A COMPUTER NETWORK, and filed on Jun. 8, 2015 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky, the contents of which are hereby incorporated by reference herein in their entirety. 
     U.S. patent application Ser. No. 15/004,904 is a non-provisional of U.S. Provisional Application No. 62/172,255, entitled METHODS AND SYSTEMS TO DETECT, PREDICT AND/OR PREVENT AN ATTACKER&#39;S NEXT ACTION IN A COMPROMISED NETWORK, and filed on Jun. 8, 2015 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky, the contents of which are hereby incorporated by reference herein in their entirety. 
     U.S. patent application Ser. No. 15/004,904 is a non-provisional of U.S. Provisional Application No. 62/172,259, entitled MANAGING DYNAMIC DECEPTIVE ENVIRONMENTS, and filed on Jun. 8, 2015 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky, the contents of which are hereby incorporated by reference herein in their entirety. 
     U.S. patent application Ser. No. 15/004,904 is a non-provisional of U.S. Provisional Application No. 62/172,261, entitled SYSTEMS AND METHODS FOR AUTOMATICALLY GENERATING NETWORK ENTITY GROUPS BASED ON ATTACK PARAMETERS AND/OR ASSIGNMENT OF AUTOMATICALLY GENERATED SECURITY POLICIES, and filed on Jun. 8, 2015 by inventors Shlomo Touboul, Hanan Levin, Stephane Roubach, Assaf Mischari, Itai Ben David, Itay Avraham, Adi Ozer, Chen Kazaz, Ofer Israeli, Olga Vingurt, Liad Gareh, Israel Grimberg, Cobby Cohen, Sharon Sultan and Matan Kubovsky, the contents of which are hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to computer security, and in particular to computer network surveillance. 
     BACKGROUND OF THE INVENTION 
     Reference is made to  FIG. 1 , which is a simplified diagram of a prior art enterprise network  100  connected to an external internet  10 . Network  100  is shown generally with resources including computers  110 , databases  120 , switches and routers  130 , and mobile devices  140  such as smart phones and tablets, for ease of presentation, although it will be appreciated by those skilled in the art that enterprise networks today are generally much more complex and include other devices such as printers, other types of network elements such as relays, and any Internet of Things objects. The various connections shown in  FIG. 1  may be direct or indirect, wired or wireless communications, or a combination of wired and wireless connections. Computers  110  and databases  120  may be physical elements or logical elements, or a mix of physical and logical elements. Computers  110  and databases  120  may be virtual machines. Computer  110  and databases  120  may be local, remote or cloud-based elements, or a mix of local, remote and cloud-based elements. Computers  110  may be client workstation computers, or server computers including inter alia file transfer protocol (FTP) servers, email servers, structured query language (SQL) servers, secure shell (SSH) servers and other application servers, or a mix of client and server computers. A corporate information technology (IT) department manages and controls network  100  in order to serve the corporate requirements and meet the corporate needs. 
     Access to computers  110  and servers  120  in network  100  may optionally be governed by an access governor  150 , such as a directory service, that authorizes users to access computers  110  and databases  120  based on “credentials”. Access governor  150  may be a name directory, such as ACTIVE DIRECTORY® developed by Microsoft Corporation of Redmond, Wash., for WINDOWS® environments. Background information about ACTIVE DIRECTORY® is available at Wikipedia. Other access governors for WINDOWS and non-WINDOWS environments, include inter alia Lightweight Directory Access Protocol (LDAP), Remote Authentication Dial-In User Service (RADIUS), and Apple Filing Protocol (AFP), formerly APPLETALK®, developed by Apple Inc. of Cupertino, Calif. Background information about LDAP, RADIUS and AFP is available at Wikipedia. 
     Access governor  150  may be one or more local machine access controllers. Access governor  150  may be one or more authorization servers, such as a database server or an application server. 
     In lieu of access governor  150 , the endpoints and/or servers of network  100  determine their local access rights. 
     Credentials for accessing computers  110  and databases  120  include inter alia server account credentials such as &lt;address&gt; &lt;username&gt; &lt;password&gt; for an FTP server, an SQL server, or an SSH server. Credentials for accessing computers  110  and databases  120  also include user login credentials &lt;username&gt; &lt;password&gt;, or &lt;username&gt; &lt;ticket&gt;, where “ticket” is an authentication ticket, such as a ticket for the Kerberos authentication protocol or NTLM hash used by Microsoft Corp., or login credentials via certificates or via another implementation used today or in the future. Background information about the Kerberos protocol and the LM hash is available at Wikipedia. 
     Access governor  150  may maintain a directory of computers  110 , databases  120  and their users. Access governor  150  authorizes users and computers, assigns and enforces security policies, and installs and updates software. When a user logs into a computer  110 , access governor  150  checks the submitted password, and determines if the user is an administrator (admin), a normal user (user) or other user type. 
     Computers  110  may run a local or remote security service, which is an operating system process that verifies users logging in to computers and other single sign-on systems and other credential storage systems. 
     Network  100  may include a security information and event management (SIEM) server  160 , which provides real-time analysis of security alerts generated by network hardware and applications. Background information about SIEM is available at Wikipedia. 
     Network  100  may include a domain name system (DNS) server  170 , or such other name service system, for translating domain names to IP addresses. Background information about DNS is available at Wikipedia. 
     Network  100  may include a firewall  180  located within a demilitarized zone (DMZ), which is a gateway between enterprise network  100  and external internet  10 . Firewall  180  controls incoming and outgoing traffic for network  100 . Background information about firewalls and DMZ is available at Wikipedia. 
     One of the most prominent threats that organizations face is a targeted attack; i.e., an individual or group of individuals that attacks the organization for a specific purpose, such as stealing data, using data and systems, modifying data and systems, and sabotaging data and systems. Targeted attacks are carried out in multiple stages, typically including inter alia reconnaissance, penetration, lateral movement and payload. Lateral movement involves orientation, movement and propagation, and includes establishing a foothold within the organization and expanding that foothold to additional systems within the organization. 
     In order to carry out the lateral movement stage, an attacker, whether a human being who is operating tools within the organization&#39;s network, or a tool with “learning” capabilities, learns information about the environment it is operating in, such as network topology and organization structure, learns “where can I go from my current step” and “how can I go from my current step (privileged required)”, and learns implemented security solutions, and then operates in accordance with that data. One method to defend against such attacks, termed “honeypots”, is to plant and monitor misleading information/decoys/bait, with the objective of the attacker learning of their existence and then consuming those bait resources, and to notify an administrator of the malicious activity. Background information about honeypots is available at Wikipedia. 
     Conventional honeypot systems operate by monitoring access to a supervised element in a computer network. Access monitoring generates many false alerts, caused by non-malicious access from automatic monitoring systems and by user mistakes. Conventional systems try to mitigate this problem by adding a level of interactivity to the honeypot, and by performing behavioral analysis of suspected malware if it has infected the honeypot itself. 
     An advanced attacker may use different attack techniques to enter a corporate network and to move laterally within the network in order to obtain its resource goals. The advanced attacker may begin with a workstation, server or any other network entity to start his lateral movement. He uses different methods to enter the first network node, including inter alia social engineering, existing exploit and/or vulnerability that he knows to exercise, and a Trojan horse or any other malware allowing him to control the first node. 
     Reference is made to  FIG. 2 , which is a simplified diagram of enterprise network  100  with attack vectors of an attacker at an early stage of lateral movement. Once an attacker has taken control of a first node in a corporate network, he uses different advance attack techniques for orientation and propagation and discovery of additional ways to reach other network nodes in the corporate network. Attacker movement from node to node is performed via an “attack vector”, which is an object in memory or storage of a first computer that may be used to access a second computer. 
     Exemplary attack vectors include inter alia credentials of users with enhanced privileges, existing share names on different servers, and details of an FTP server, an email server, an SQL server or an SSH server and its credentials. Attack vectors are often available to an attacker because a user did not logoff his workstation or clear his cache. E.g., if a user contacted a help desk and gave the help desk remote access to his workstation and did not logoff his workstation, then the help desk access credentials may still be stored in the user&#39;s local cache and available to the attacker. Similarly, if the user accessed an FTP server, then the FTP account login parameters may be stored in the user&#39;s local cache or profile and available to the attacker. 
     Attack vectors enable inter alia a move from workstation A→server B based on a shared name and its credentials, connection to a different workstation using local admin credentials that reside on a current workstation, and connection to an FTP server using specific access credentials. 
     Reference is made to  FIG. 3 , which is a simplified diagram of enterprise network  100  with attack paths of an attacker at a later stage of lateral movement. Whereas IT “sees” the logical and physical network topology, an attacker that lands on the first network node “sees” attack vectors that depart from that node and move laterally to other nodes. The attacker can move to such nodes and then follow “attack paths” by successively discovering attack vectors from node to node. 
     When the attacker implements such a discovery process on all nodes in the network, he will be able to “see” all attack vectors of the corporate network and generate a “maximal attack map”. Before the attacker discovers all attack vectors on network nodes and completes the discovery process, he generates a “current attack map” that is currently available to him. 
     An objective of the attacker is to discover an attack path that leads him to a target network node. The target may be a bank authorized server that is used by the corporation for ordering bank account transfers of money, it may be an FTP server that updates the image of all corporate points of sale, it may be a server or workstation that stores confidential information such as source code and secret formulas of the corporation, or it may be any other network node that is of value to the attacker and is his “attack goal node”. 
     When the attacker lands on the first node, but does not know how to reach the attack goal node, he generates a current attack map that leads to the attack goal node. 
     SUMMARY 
     There is thus provided in accordance with an embodiment of the present invention a system for network surveillance to detect attackers, including a deception management server within a network of resources, including a deployment module managing and planting one or more decoy attack vectors in one or more of the resources in the network, wherein an attack vector is an object in memory or storage of a first resource that may be used to access a second resource, and one or more decoy servers accessible from resources in the network via one or more of the decoy attack vectors planted in the resources by the deployment module, each decoy server including a forensic alert module causing a real-time forensic application to be transmitted to a destination resource in the network when the decoy server is being accessed by a specific resource in the network via one or more of the decoy attack vectors planted in the specific resource by the deployment module, wherein the forensic application, when launched in the destination resource, identifies a process running within the specific resource that is accessing that decoy server, logs the activities performed by the thus-identified process in a forensic report, and transmits the forensic report to the deception management server. 
     There is additionally provided in accordance with an embodiment of the present invention a method of network surveillance to detect attackers, including planting one or more decoy attack vectors in one or more resources in a network of computers, wherein an attack vector is an object in memory or storage of a first resource that may be used to access a second resource, recognizing that a decoy server in the network is being accessed by a specific resource in the network via one or more of the decoy attack vectors planted in the specific resource by the planting, and causing a real-time forensic application to be transmitted to a destination resource, wherein the forensic application, when launched on the destination resource, is operative to identify a process running within the specific resource that is accessing the decoy server, log the activities performed by the thus-identified process in a forensic report, and transmit the forensic report to a deception management server. 
     There is further provided in accordance with an embodiment of the present invention a system for network surveillance to detect attackers, the system including a deception management server within a network of resources that is governed by an access governor that authorizes users to access the resources in the network based on user credentials, the deception management server including a deployment module, planting one or more decoy user credentials in one or more of the resources in the network, and a forensic alert module for causing a real-time forensic application to be transmitted to a destination resource in the network, in response to the access governor recognizing an attempt by a first resource to access a second resource in the network via one or more of the decoy credentials planted in the first resource by the deployment module, wherein the forensic application, when launched in the destination resource, identifies a process running within the first resource that is attempting to access the second resource, logs the activities performed by the thus-identified process in a forensic report, and transmits the forensic report to the deception management server. 
     There is yet further provided in accordance with an embodiment of the present invention a method of network surveillance to detect attackers, including planting one or more decoy user credentials in one or more resources in a network of resources that is governed by an access governor that authorizes users to access the resources in the network based on user credentials, recognizing an attempt by a first resource in the network to access a second resource in the network via one or more of the decoy user credentials planted in the first resource by the planting, and in response to the recognizing, causing a real-time forensic application to be transmitted to a destination resource, wherein the forensic application, when launched, is operative to identify a process running within the first resource that is accessing the decoy server, log the activities performed by the thus-identified process, and transmit the log to a deception management server. 
     There is moreover provided in accordance with an embodiment of the present invention a system for network surveillance to detect attackers, including a deception management server located within a network of resources, the network being governed by an access governor that authorizes users to access the resources in the network based on credentials that include a hash version of a cleartext password, the deception management server including a deployment module, planting one or more decoy credentials in one or more of the resources in the network, and a forensic alert module causing a real-time forensic application to be transmitted to a destination resource in the network, in response to recognizing that a first resource in the network attempts to access a second resource in the network using a decoy credential with its cleartext password, wherein the forensic application, when launched in the destination computer, identifies a process running within the first resource that is attempting to access the second resource, logs the activities performed by the thus-identified process in a forensic report, and transmits the forensic report to the deception management server. 
     There is additionally provided in accordance with an embodiment of the present invention a method of network surveillance to detect attackers, including planting a decoy credential in a first resource, wherein a credential enables a user to access a resource via a password, and wherein the decoy credential includes a hash of a cleartext password for accessing a second resource, recognizing that the first resource attempts to access the second resource using the cleartext password of the decoy credential, and causing, in response to the recognizing, a real-time forensic application to be transmitted to a destination computer, wherein the forensic application, when launched, is operative to identify a process running within the first resource that is attempting to access the second resource, log the activities performed by the thus-identified process, and transmit the log to a deception management server. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings in which: 
         FIG. 1  is a simplified diagram of a prior art enterprise network connected to an external internet; 
         FIG. 2  is a simplified diagram of a prior art enterprise network with attack vectors of an attacker at an early stage of lateral movement; 
         FIG. 3  is a simplified diagram of a prior art enterprise network with attack paths of an attacker at a later stage of lateral movement; 
         FIG. 4  is a simplified diagram of an enterprise network with network surveillance, in accordance with an embodiment of the present invention; 
         FIG. 5  is a simplified flowchart of a method for network surveillance and notification using decoy servers, in accordance with an embodiment of the present invention; 
         FIG. 6  is a simplified method for network surveillance and notification using decoy user credentials, in accordance with an embodiment of the present invention; and 
         FIG. 7  is a simplified diagram of a method for network surveillance using two-factor deception, in accordance with an embodiment of the present invention. 
     
    
    
     For reference to the figures, the following index of elements and their numerals is provided. Similarly numbered elements represent elements of the same type, but they need not be identical elements. 
     
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 Table of elements in the figures 
               
             
          
           
               
                 Element 
                 Description 
               
               
                   
               
             
          
           
               
                 10 
                 Internet 
               
               
                 100 
                 enterprise network 
               
               
                 110 
                 network computers 
               
               
                 120 
                 network databases 
               
               
                 130 
                 network switches and routers 
               
               
                 140 
                 mobile devices 
               
               
                 150 
                 access governor (optional) 
               
               
                 160 
                 SIEM server 
               
               
                 170 
                 DNS server 
               
               
                 180 
                 firewall 
               
               
                 200 
                 enterprise network with network surveillance 
               
               
                 210 
                 deception management server 
               
               
                 211 
                 policy manager 
               
               
                 212 
                 deployment module 
               
               
                 213 
                 forensic application 
               
               
                 220 
                 database of credential types 
               
               
                 230 
                 policy database 
               
               
                 240 
                 decoy servers 
               
               
                 241 
                 tar-pit modules 
               
               
                 242 
                 forensic alert module 
               
               
                 250 
                 update server 
               
               
                   
               
             
          
         
       
     
     Elements numbered in the 1000&#39;s are operations of flow charts. 
     DETAILED DESCRIPTION 
     In accordance with embodiments of the present invention, systems and methods are provided for creating, deploying and managing augmentation to an attacker&#39;s current attack map. These systems and methods define decoy attack vectors that change the current attack map, and detect the attacker when he follows an attack vector that leads to a decoy network node. 
     Reference is made to  FIG. 4 , which is a simplified diagram of an enterprise network  200  with network surveillance, in accordance with an embodiment of the present invention. Network  200  includes a deception management server  210 , a database  220  of decoy attack vectors, a policy database  230  and decoy servers  240 . In addition, network computers  110  and databases  120  are grouped into groups G 1 , G 2 , G 3  and G 4 . 
     Database  220  stores attack vectors that fake movement and access to computers  110 , databases  120  and other resources in network  200 . Attack vectors include inter alia:
     user credentials of the form &lt;username&gt; &lt;password&gt;   user credentials of the form &lt;username&gt; &lt;hash of password&gt;   user credentials of the form &lt;username&gt; &lt;ticket&gt;   FTP server credentials of the form &lt;address&gt; &lt;username&gt; &lt;password&gt;   SSH server credentials of the form &lt;address&gt; &lt;username&gt; &lt;password&gt;   

     The attack vectors stored in database  220  are categorized by families, such as inter alia
     F 1 —user credentials   F 2 —connections   F 3 —FTP logins   F 4 —SSH logins   F 5 —share names   F 6 —databases   F 7 —network devices   F 8 —URLs   F 9 —Remote Desktop Protocol (RDP)   F 10 —recent command   F 11 —scanners   

     Credentials for a computer B that reside on a computer A provide an attack vector for an attacker from computer A→computer B. 
     Database  220  communicates with an update server  250 , which updates database  220  as attack vectors for accessing, manipulating and hopping to computers evolve over time. 
     Policy database  230  stores, for each group of computers, G 1 , G 2 , . . . , policies for planting decoy attack vectors in computers of that group. Each policy specifies decoy attack vectors that are planted in each group, in accordance with attack vectors stored in database  220 . For user credentials, the decoy attack vectors planted on a computer lead to another resource in the network. For attack vectors to access an FTP or other server, the decoy attack vectors planted on a computer lead to a decoy server  240 . 
     It will be appreciated by those skilled in the art the databases  220  and  230  may be combined into a single database, or distributed over multiple databases. 
     Deception management server  210  includes a policy manager  211 , a deployment module  212 , and a forensic application  213 . Policy manager  211  defines a decoy and response policy. The response policy defines different decoy types, different decoy combinations, response procedures, notification services, and assignments of policies to specific network nodes, network users, groups of nodes or users or both. Once policies are defined, they are stored in policy database  230  with the defined assignments. 
     Deception management server  210  obtains the policies and their assignments from policy database  230 , and delivers them to appropriate nodes and groups. It than launches deployment module  212  to plant decoys in end points, servers, applications, routers, switches, relays and other entities in the network. Deployment module  212  plants each decoy, based on its type, in memory (RAM), disk, or in any other data or information storage area, as appropriate. Deployment module  212  plants the decoy attack vectors in such a way that the chances of a valid user accessing the decoy attack vectors are low. Deployment module  212  may or may not stay resident. 
     Forensic application  213  is a real-time application that is transmitted to a destination computer in the network, when a decoy attack vector is accessed by a computer  110 . When forensic application  213  is launched on the destination computer, it identifies a process running within that computer  110  that accessed that decoy attack vector, logs the activities performed by the thus-identified process in a forensic report, and transmits the forensic report to deception management server  210 . 
     Once an attacker is detected, a “response procedure” is launched. The response procedure includes inter alia various notifications to various addresses, and actions on a decoy server such as launching an investigation process, and isolating, shutting down and re-imaging one or more network nodes. The response procedure collects information available on one or more nodes that may help in identifying the attacker&#39;s attack acts, attention and progress. 
     Each decoy server  240  includes a tar-pit module  241 , which is a process that purposely delays incoming connections, thereby providing additional time for forensic application  213  to launch and log activities on a computer  110  that is accessing the decoy server. Each decoy server  240  also includes a forensic alert module  242 , which alerts management system  210  that an attacker is accessing the decoy server via a computer  110  of the network, and causes deception management server  210  to send forensic application  213  to the computer that is accessing the decoy server. In an alternative embodiment of the present invention, decoy server  240  may store forensic application  213 , in which case decoy server  240  may transmit forensic application  213  directly to the computer that is accessing the decoy server. In another alternative embodiment of the present invention, deception management server  210  or decoy server  240  may transmit forensic application  213  to a destination computer other than the computer that is accessing the decoy server. 
     Notification servers (not shown) are notified when an attacker uses a decoy. The notification servers may discover this by themselves, or by using information stored on access governor  150  and SIEM  160 . The notification servers forward notifications, or results of processing multiple notifications, to create notification time lines or such other analytics. 
     Reference is made to  FIG. 5 , which is a simplified flowchart of a method  1100  for network surveillance and notification using decoy servers, in accordance with an embodiment of the present invention. The flowchart of  FIG. 5  is divided into three columns. The leftmost column includes operations performed by deception management server  210 . The middle column includes operations performed by a decoy server B that is accessed from a computer A using decoy attack vectors. The rightmost column includes operations performed by computer A. 
     At operation  1105 , deployment module  212  plants decoy attack vectors in computers  110  in accordance with the policies in database  230 . At operation  1110  decoy server B recognizes that it is being accessed from a computer A via a decoy attack vector. At operation  1115 , tar-pit module  241  of decoy server B delays access to data and resources on decoy server B. The delaying performed at operation  1115  provides additional time for decoy server B to send a request to deception management server  210  to transmit forensic application  213  to computer A, and for computer A to receive and run forensic application  213 . At operation  1120 , decoy server B sends a request to deception management server  210 , to transmit real-time forensic application  213  to computer A. 
     At operation  1125 , deception management server  210  receives the request send by decoy server B, and at operation  1130  deception management server  210  transmits forensic application  213  to computer A. 
     At operation  1135 , computer A receives forensic application  213  from deception management server  210 , and launches the application. At operation  1140 , forensic application  213  identifies a process, P, running on computer A that is accessing decoy server B. At operation  1145 , forensic application  213  logs activities performed by process P. At operation  1150 , forensic application  213  transmits a forensic report to deception management server  210 . Finally, at operation  1155 , deception management server  210  receives the forensic report from computer A. 
     In accordance with an alternative embodiment of the present invention, decoy server B may store forensic application  213 , in which case decoy server B may transmit forensic application  213  directly to computer A, and operations  1120 ,  1125  and  1130  can be eliminated. 
     In accordance with another alternative embodiment of the present invention, forensic application  213  is transmitted by deception management server  210  or by decoy server B to a destination computer other than computer A. When the destination computer launches forensic application  213 , the application communicates with computer A to identify the process, P, running on computer A that is accessing decoy server B, log the activities performed by process P, and transmit the forensic report to deception management server  210   
     Reference is made to  FIG. 6 , which is a simplified method for network surveillance and notification using decoy user credentials, in accordance with an embodiment of the present invention. The flowchart of  FIG. 6  is divided into three columns. The leftmost column includes operations performed by deception management server  210 . The middle column includes operations performed by access governor  150 . The rightmost column includes operations performed by a computer A that attempts to login to a computer B using decoy user credentials. 
     At operation  1205 , deployment module  212  plants decoy credentials in computers  110  in accordance with the policies in database  230 . At operation  1210  access governor  150  receives an authorization request from a computer B for a login to a computer A using invalid user credentials. At operation  1215  access governor  150  reports the attempted invalid login to SIEM server  160 . 
     At operation  1225 , deception management server  210  identifies an invalid login attempt event reported by SIEM server  160 , and at operation  1230  deception management server  210  transmits real-time forensic application  213  to computer A. 
     At operation  1235 , computer A receives forensic application  213  from deception management server  210 , and launches the application. At operation  1240 , forensic application  213  identifies a process, P, running on computer A that is accessing computer B. At operation  1245 , forensic application  213  logs activities performed by process P. At operation  1250 , forensic application  213  transmits a forensic report to deception management server  210 . Finally, at operation  1255 , deception management server  210  receives the forensic report from computer A. 
     In accordance with an alternative embodiment of the present invention, forensic application  213  is transmitted by deception management server  210  to a destination computer other than computer A. When the destination computer launches forensic application  213 , the application communicates with computer A to identify the process, P, running on computer A that is accessing computer B, log the activities performed by process P, and transmit the forensic report to deception management server  210   
     As mentioned above, conventional honeypot systems generate many false alerts. Embodiments of the present invention enhance confidence levels in identifying an attacker, by luring him into multiple access attempts to different resources monitored by the system. 
     Reference is made to  FIG. 7 , which is a simplified diagram of a method for network surveillance using two-factor deception, in accordance with an embodiment of the present invention. At operation  1310  an attacker accesses a computer A of network  200 . At operation  1320  the attacker obtains decoy credentials for accessing a computer B of network  200 , the decoy credentials being of the form &lt;username&gt; &lt;hash&gt;, where &lt;hash&gt; is a hash value of a cleartext password. The decoy credentials are preferably planted in computer A such that the chances of a valid user or automated monitor accessing the credentials are low. 
     At operation  1330  the attacker derives the cleartext password from &lt;hash&gt;. Operation  1330  may be performed by rainbow tables, which are pre-computed tables for reversing cryptographic hash functions. At operation  1340  the attacker attempts a login to computer B using the cleartext version of the decoy credentials &lt;username&gt; &lt;cleartext password&gt;. At this stage, the chances of such login being performed by a valid user or automated monitor are extremely low, since this login requires two suspicious factors; namely, (i) extracting the decoy credentials with the hash value of the cleartext password from computer A, and (ii) reversing the extracted hash value to obtain the cleartext password. 
     It will be appreciated by those skilled in the art that the two-factor method shown in  FIG. 7  can be extended to more than two factors by successively planting a trail of decoy credentials that lead from one computer to the next. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific exemplary embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.