## 3 CISS2021-OL Attacks  
The two Red Team sessions mentioned in Section 2.3, launched a total of 27 successful attacks listed in Tables 2-8. Attacks listed in the table are typed as follows: SSSP-Single Stage Single Point attack; SSMP-Single Stage Multi Point attack; and MSMP-Multi Stage Multi Point. Here, \"stage\" refers to one of the six stages of SWaT and \"point\" to a target. Each device in the plant is associated with a unique identifier tag. The tags are AIT: chemical sensor, FIT: flow rate sensor, LIT: level sensor, MV: motorized valve, P: pump, and T: tank. A sample of these attacks are described below. 1. A4: Drain water from the UF process: In this attack, the attacker intended to manipulate the status of the actuators in stage 3 to drain water during the ultrafiltration process. This attack was executed in two steps. First, PLC3 was set to manual mode wherein the operator could directly control the actuator status. In the second step, the measurement from level sensor LIT301 was set to 1100 mm, and valves MV301 and MV302 valves were closed. Subsequently, the attackers opened valve MV303 and switched on the pumps P301 and P302. 2. A7: Control the chemical dosing system: The attacker intended to degrade the water quality by disrupting the chemical dosing system. The attackers changed the commands sent, and measurements received, by PLC2. First, all pumps in stage 2 were started, and valves MV201 and MV301 opened. Subsequently, measurements from chemical sensors AIT201 (conductivity), AIT202 (pH), and AIT203 (ORP) received by the PLC2 were set to 69, 11, and 111, respectively. 3. A17: Disrupt the RO process: The attacker intended to exploit the vulnerabilities in the SCADA workstation to redirect water from the RO process to the UF backwash tank. A cyber-criminal attacker model was designed to launch this attack. Using Metasploit [8], the attacker exploited the Windows-7 vulnerabilities to retrieve various login credentials. Using administrative credentials and RDP [9], the attacker gained access to the SCADA workstation to control the entire plant. Using SCADA's user interface, the attacker manually closed all valves in stage 5, except MV503 and MV504, thereby redirecting water from the RO process to the UF backwash tank. 4. A22: Manipulating the valves to disturb the raw water tank filling process: The objective of this attack was to stop the inflow of raw water into tank T101 for 2 min. To realize the objective, MV101 was set to manual mode and closed. 5. A25: Damage the water pumps: The objective of this attack was to damage the water pumps that transfer water from the raw water tank to stage 2. The attackers alternately opened and closed pumps P101 and P102. Attacks and anomaly: Note that AICrit is designed to detect process anomalies. Thus, any attack that causes an abnormal change in the water treatment process, ought to be detected by AICrit. However, there could be attacks wherein the physical process might not deviate from its normal operation. An example of such an attack is one intended to crash the historian server. Such an attack will not be detected by ACrit because, as in this case, the detector stops receiving plant state. This example is illustrative of the importance of the location, and the limitations, of an anomaly detector in a plant.