This undated US law enforcement handout photo shows Albert Gonzalez. The American man who stole millions of credit card numbers in one of the biggest computer hacking operations in US history was sentenced Thursday to 20 years prison.

(AP) -- A computer hacker from Florida was sentenced Thursday to 20 years in prison for helping engineer one of the largest thefts of credit and debit card numbers in U.S. history.

U.S. Patti Saris sentenced Albert Gonzalez of Miami, who pleaded guilty last year to breaking into computer systems of major retailers, including TJX Cos. and BJ's Wholesale Club.

Prosecutors had sought 25 years for Gonzalez, saying he victimized millions of people and cost companies, banks and insurers nearly $200 million. His lawyer had argued Gonzalez should get no more than 15 years.

Gonzalez pleaded guilty last year in three separate hacking cases brought in Massachusetts, New Jersey and New York. The Thursday hearing dealt with the Massachusetts case. A second sentencing Friday, also in Boston, will deal with the others.

Gonzalez's Boston attorney, Martin Weinberg, has said his client, a self-taught computer genius, displayed behavior consistent with Asperger's syndrome, a form of autism. A defense psychiatrist's report described Gonzalez as a socially awkward Internet addict with an "idiot-savant-like genius for computers and information technology."

Authorities said Gonzalez and two foreign co-defendants would drive past retailers with a , tapping into those with vulnerable signals. They would then install "sniffer programs" that picked off credit and debit card numbers as they moved through a retailer's computers before trying to sell the numbers overseas, authorities said.

Gonzalez, known online as "soupnazi," became a Secret Service informant after he was first arrested for hacking in 2003.

But even as he helped the government nail other hackers, prosecutors said, he kept breaking into retailers' computer systems, amassing $2.8 million he used to buy a Miami condo, a car, Rolex watches and a Tiffany ring for his girlfriend.