A cyber-security incident that impacted a US power grid entity earlier this year was not as dangerous as initially thought, the North American Electric Reliability Corporation (NERC) said last week.

In a report highlighting the “lessons learned” from a past incident, NERC said hackers repeatedly caused firewalls to reboot for about ten hours, on March 5, 2019.

The incident impacted firewalls deployed at multiple power generation sites operated by a “low-impact” operator and did not cause any disruption in the electric power supply.