Vulnerable Protection Relays Put Power Grid at Risk

Google’s Mandiant Warns About Remote Attacks Disrupting Grid Stability Prajeet Nair (@prajeetspeaks) • July 2, 2025

Vulnerabilities in networked devices programmed to instantaneously trip power grid substation circuit breakers could be the means hackers use to cause the next blackout, warn researchers.

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Protection relays - devices that continually monitor voltage, current, frequency and phase angle - are "the brains of both protection and control" at the site where high voltage lines meet lower-voltage residential lines, said Google-owned Mandiant in a Monday blog post. Should protection relays detect a problem such as ground fault, they react within 20 milliseconds to trip circuit breakers. Simulated attacks conducted by Mandiant consistently reveal insecure remote pathways into local substation networks.

Substations may appear as the last bastion of a fully analog world, humming behind a ...