Are squirrels a bigger threat to the power grid than hackers?:
They can strike at almost any moment – gnawing through the insulation guarding power lines or burrowing into substations in risky missions that can leave thousands without power at a time. The bushy-tailed rodent has even sparked economic mayhem: Back in 1987, a rogue squirrel took out the power to a NASDAQ computer center for nearly an hour and half, stopping an estimated 20 million shares from being traded, according to the New York Times.
The critters are such a big problem that the American Public Power Association even tracks the blackouts they cause with its own “Squirrel Index.”