Protection against False Data Injection Attacks Considering Degrees of Freedom in Attack Vectors

In a false data injection attack to compromise the results of state estimation, the attacker intends to alter the meter readings communicated to the control center to his/her desired values to realize an objective. However, to avoid detection, the manipulated readings should not violate physical laws. Therefore, even if an attacker is able to attack a set of meters, he/she may not be able to inject an arbitrary magnitude of attack into all meters of this set. In this paper, we study the degrees of freedom in the attack vectors available to the attacker; higher degrees of freedom pose a higher risk to the utility. We propose an algorithm to determine the degrees of freedom in attack vectors and a method to find the set of meters to be secured in order to minimize the degrees of freedom in all attack vectors. Our results show that a significant reduction in degrees of freedom in all attack vectors is possible by securing a small set of meters.