# Survey of Cybersecurity Governance, Threats, and Countermeasures for the Power Grid +
## 4 Cybersecurity Threats in Energy System OT Networks
### Availability Threats  
In DoS attacks, the perpetrator seeks to make information or operational technology systems unavailable, either temporarily or indefinitely, to authorized users or other systems in the network. For instance, this may be accomplished in traditional IT by overloading a web service with superfluous requests. In OT systems, there may be unique attack vectors for carrying out DoS attacks compared to IT systems. For instance, perpetrators of DoS attacks may target systems or data that are critical for correct operation of automated control systems. DoS attacks represent significant threats to power systems because the control systems in such systems are sensitive to timing and any disruption to critical information can compromise the entire system's availability. As explained in [13], there are several different taxonomies of DoS attacks in the Smart Grid. They can be classified by vulnerabilities in common SG communications protocols, by major SG applications, or by attacker exploitation techniques. With regards to exploitation techniques, the major categories are jamming [18; 28; 29; 30; 31], resource exhaustion [32; 33; 34; 35; 36; 37; 38], cryptography algorithm exploits [39], data attacks, de-synchronization attacks [40; 41], routing-based attacks, and reflector attack. Jamming attacks are a form of DoS attack, and present a significant threat to the availability of smart grid systems. In jamming attacks, the shared nature of wireless channels is exploited by sending a continuous flow of data to prevent legitimate users from utilizing the channel. The authors in [42] propose a jamming channel attack called Maximum Attacking Strategy using Spoofing and Jamming (MAS-SJ). This attack targets PMUs of the cognitive radio network (CRN) used for providing time-synchronized data of power operating states in a wireless smart grid network (WSGN). In [32; 37], the authors introduce the puppet attack, where a vulnerability in the Advanced Metering Infrastructure (AMI) dynamic source routing protocol is exploited, causing the network bandwidth to become exhausted. In [43], the Time-Delay-Switch (TDS) attack is proposed, where attackers introduce time delays into control loops to cause general instability of the smart grid system. The Time Synchronization Attack (TSA) [40] targets the integrity of the GPS information of Phasor Measurement Units (PMUs) of various smart grid applications, including transmission line fault detection, voltage stability monitoring, and event locationing. In [44], the effects of flooding attacks on time-critical communications of the Smart Grid are explored. Another potential threat against availability and integrity are wormhole attacks, as shown in [45]. Attacks that primarily target data integrity may impact their availability as well. In power grid applications, the false data injection attack [40] is a well-known example of this. In FDIA, the power grid state-estimation systems are targeted in order to distort real energy supply and demand figures, which may cause blackouts, physical damage, or even the loss of human lives [18]. FDIA attacks may also effectively become a denial-of-service attack as they may cause critical services to become unavailable. The research of detection strategies for FDIA is a highly active area, because it carries the potential for large impact and benefits to a very challenging problem. Due to the time-sensitive nature of the communications involved in these state-estimation systems, detection schemes must be very efficient. Some additional attacks that target data integrity that may lead to DoS are presented in [46; 47; 48]. Some basic attacks may have a large impact on availability as well. Viruses, worms, and trojan horses pose a significant threat to IT and OT systems, not only in terms of availability, but in terms integrity and confidentiality as well. The Stuxnet worm and Duqu malware [37] are two examples of such attacks. These attacks may be able to bypass any existing defense-in-depth strategies, which makes them particularly dangerous.