NEW YORK - A temporary worker at Goldman Sachs & Co. and Credit Suisse First Boston passed on confidential information about 23 mergers and other transactions to friends and investors he met in an Internet chat room, federal prosecutors said Tuesday.

In a case authorities call "one of the largest insider trading schemes ever prosecuted," U.S. Attorney Mary Jo White said John Freeman gained access to inside information as a part-time computer graphics worker at the two companies. Those assignments required him to create or revise documents related to mergers, prosecutors said.

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