Recovery of Discrete Event Systems After Active Cyberattacks

In active cyberattacks, an intruder can alter the nominal system behavior to cause damage to devices and/or users. Although many works in the literature propose techniques to mitigate active attacks from the perspective of the discrete event supervisory control system, there is limited discussion on the recovery of the system’s nominal behavior after an attack is detected and isolated by a cyberdefense mechanism. In this letter, we formulate a recovery structure and define a recoverability property, based on which we propose a method for the synthesis of a nonblocking supervisory control that drives the discrete event system from a state estimate after an extinguished attack back to its nominal closed-loop behavior in a finite number of observations while avoiding unsafe states.