DNAttest: Digital-twin-based Non-intrusive Attestation under Transient Uncertainty.

Programmable logic controllers (PLCs) are vulnerable to malware, which is a key security risk for Industrial Control Systems (ICSs). Existing attestation solutions are invasive because they require hardware security modules and software upgrades in legacy devices. We propose DNAttest, a Digital-twin-based Non-invasive Attestation solution to attest PLC behaviors in near-real time. DNAttest requires minimal ICS infrastructure changes and does not interfere with normal ICS operations. DNAttest detects PLC deviations by replicating all input messages for a PLC to its digital twin and comparing their output messages. Due to transient uncertainty in the PLC's internal processing state, DNAttest may output an incorrect comparison. To generate all plausible output values for comparison, we instantiate multiple emulated PLCs by replicating input messages with different timing profiles. We demonstrate on a close-to-real-world power grid testbed that DNAttest can provide a timely detection of a wide range of attacks non-invasively and accurately. DNAttest solution is lightweight and scalable. A typical desktop PC can attest more than 20 actual PLCs even if we use 10 emulators to monitor every actual PLC.