In March of this year, a cyber incident affected firewalls at multiple power generation sites across the US. According to a recent report by the North American Electric Reliability Corporation (NERC), the attack was less serious than initially thought, and did not significantly impact electricity supply.

The attackers exploited “a known firewall vulnerability,” that enabled them to force firewalls at the network perimeter to reboot at short intervals over a period of around 10 hours until the operator installed security patches to fix the issue. The operator has since streamlined the firmware patch management process.

Read more: Cyber-security incident at US power grid entity linked to unpatched firewalls