A former network administrator US has pleaded guilty to hacking and ID theft charges.
Andrew Madrid now faces up to 12 years in prison after using his IT skills to pull off a variety of crimes between September 2006 and March 2008.
"This was one of the most sophisticated computer crimes our office has prosecuted," said Ben Field, a deputy district attorney in Santa Clara in the US.
"There's computer intrusion in the first place, there's the introduction of spyware, there's the theft of proprietary data from a computer network, and sometimes the destruction of proprietary data from a computer network."
One of Madrid's victims was his former employer. Madrid destroyed data on the company's servers in the hope that "they would ask him to come back and fix the very problem that he created."
Madrid would often use his neighbour's open wireless networks and even posed as a security guard or an IT person, to enter premises late at night looking for laptops and other computer equipment to steal.
"He had a good eye for what was valuable," Field said.
If stopped by company employees, "he would talk to them as if he was completely justified in being there", Field said. "Like he was an IT person doing some work or a security guard making sure the place was secure."
"Being a former network administrator, he could talk the talk as an IT guy," he added.