William Carl Shea, 39, who worked in Silicon Valley was unhappy after being put on a performance improvement plan by his employer.
According to the prosecution Shea was reprimanded near the end of 2002 and placed on the improvement program on January 6, 2003. By January 17 Shea had stopped turning up for work.
In the intermittent period Shea had planted software designed to delete financial records and disrupt the operations of the debt collection company. The malware time bomb remained undetected until, at the end of January, it exploded. In all 50,000 records were affected by Shea's work.
The maximum penalty Shea faces is five years in prison and a $250,000 fine. Sentencing will begin on November 21 in San Jose.
In July SC reported an Australian software developer could be out of a job after a court found he may have intended to share trade secrets about multi-million deal involving telcom provider Telstra.