Two US power stations were infected by malware in the last quarter of 2012, according to a report by the US Department of Homeland Security's Industrial Control Systems Cyber Emergency Response Team (ICS-CERT).

USB flash drives packed with software nasties were blamed for a compromise of industrial control systems in both cases. Neither infected power plant was named.

The first case emerged after a maintenance engineer noticed the thumb drive he used to back up control system settings had become unreliable. The worker then referred the matter to the IT department, which found three infections on the gadget.

Investigators found sophisticated although unspecified malware on two engineering workstations associated with running critical applications. The subsequent cleanup operation was complicated by a lack of backups.

The second infection was blamed on a third-party contractor who unwittingly poisoned systems at a power generation utility after plugging in an infected USB drive at work. A "crimeware" virus got into a turbine control system and hit approximately 10 computers on its network. The subsequent cleanup delayed a plant restart operation by about three weeks, the report said.

ICS-CERT highlights cases as a means to educate other power station operators about the risk of malware in industrial control system environments. More details on both cases, along with information about proactive research by ICS-CERT into SCADA security, can be found in a quarterly report here (PDF). ®