You Snooze, You Lose: Measuring PLC Cycle Times under Attacks

In this work, we show that the electrical side of a Programmable Logic Controller (PLC), that is, the controlled process, can be influenced by packet flooding. This differs from already known Denial of Service (DoS) attacks as the target is the actual process and not network connectivity. We conducted our experiments with 16 devices from six vendors, giving a good overview of the current market. Except for one device, all are susceptible to network flooding attacks. In three cases, an attack even lead to a DoS on the electrical side, completely disrupting any controlled process. In addition, we show that well-known scanning tools have measurable impacts on PLCs. These findings should be taken into consideration by administrators and researchers planning scanning activities.