Albert Gonzalez, the hacker who pleaded guilty to one of the largest cases of credit card theft in the U.S.. Gonzalez, was sentenced to 20 years in federal prison last month after he confessed to stealing millions of credit and debit card numbers from major retailers, including T.J.Maxx, BJ’s Wholesale Club, Office Max, Barnes & Noble, Hannaford Bros., and Heartland Payment Systems.

He was accused of breaking into systems by wardriving a technique using a laptop to detect an unsecured wireless networks and then installing sniffer programs to capture un suspecting data. The data was then used to make clone cards and withdraw cash from ATMs.

Gonzalez then allegedly encoded the data onto the magnetic stripes of blank cards, and sold the credit numbers, or used the new cards to withdraw tens of thousands of dollars at a time from ATMs. Prosecutors also claim that Gonzales allegedly concealed and laundered the proceeds by using Internet-based currencies, and by channeling money through bank accounts in Eastern Europe.