A sysadmin last week pleaded guilty to attempting to disrupt the power grid in California by shutting down a data center that managed the state's electricity supply.

Lonnie Charles Denison, 33, of South Natomas in California confessed to breaking a glass cover and pushing an emergency power off button at the Independent System Operator's (ISO) data center near Folsom on 15 April. The contract Unix sysadmin was upset with his employer and co-workers at the time. Denison reportedly snapped shortly after discovering his computer privileges had been revoked.

His actions prevented the ISO from communicating with the electricity market for about two hours, leaving California vulnerable to blackout conditions. In the event no blackout occurred because the incident happened late on a Sunday night, when demand was low, so California had no need to buy in excess generating capacity from other states.

Nonetheless, the incident cost the centre $14,000, UPI reports. It took 20 computer specialists about seven hours to restore the system.

Folsom data centre blues

Prosecutors allege Denision compounded his offences by sending a threatening email to an unnamed California ISO employee the next day implying he planted a bomb at the facility. The email said: "Hey, at one point I respected you... you have a new kid. So this is only because of him. Get out before the timer expires. Not long now. Take care."

ISO responded by evacuating 500 workers from the facility and transfered control of the grid to a second control centre.

Denison pleaded guilty to attempted damage of an energy facility, a felony offence punishable with up to five years' imprisonment and a $250,000 fine, at a hearing in Sacremento on Friday. The rogue employee faces a sentencing hearing scheduled for 29 February. ®