Federal prosecutors credited the man responsible for transmitting the Melissa virus — a computer bug that did more than $80 million (U.S.) in damage in 1999 — with helping the FBI bring down several major international hackers.

Court documents unsealed Wednesday at the request of The Associated Press show that David Smith began working with the FBI within weeks of his 1999 arrest, primarily using a fake identity to communicate with and track hackers from around the world.

“Smith provided timely, substantial assistance to the United States in the investigation and prosecution of others,” New Jersey's U.S. Attorney, Christopher J. Christie, wrote to federal judge Joseph Greenaway in an April 2002 letter.

Mr. Greenaway, who could have sentenced Mr. Smith to about 10 years in prison under federal sentencing guidelines, reduced the sentence to 20 months after reading the letter.

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