A former discount furniture salesman is now an FBI cyber expert who has been credited with taking down some of the world’s leading hackers.

Supervisory Special Agent J. Keith Mularski joined the FBI in 1998 and the Pittsburgh office’s cyber squad in 2005.

In May, he helped prosecutors charge five Chinese Army intelligence officers with stealing trade secrets from companies like U.S. Steel and Westinghouse. A month later, a Russian man was charged with leading a worldwide identity theft ring that infected 350,000 computers and used the stolen information to steal $100 million.

He made his reputation by infiltrating a forum that allowed crooks to buy and sell stolen credit card information. He used the screen name “Master Splyntr,” a takeoff on the cartoon rat who guides the Teenage Mutant Ninja Turtles.

(AP)