In what it is calling Operation Phish Phry, the F.B.I. began arresting 53 people on Wednesday on charges of conducting a vast financial fraud based on phishing  the act of tricking Internet users into revealing their passwords and other information.

The arrests were in Southern California, Nevada and North Carolina, while the authorities in Egypt sought to arrest 47 people whom the F.B.I. said were co-conspirators.

An 86-page indictment, filed in the United States District Court for the Central District of California in Los Angeles, accuses the defendants of tricking people into giving up their bank account information. The F.B.I. said that this was the largest number of defendants ever charged in a cybercrime case, and that they had stolen at least $2 million from 2007 to last month.

The scams victimized people with accounts at Bank of America and Wells Fargo, two of the nation’s largest banks. The online component of the fraud was perpetrated in Egypt, Keith B. Bolcar, the acting chief of the F.B.I.’s Los Angeles bureau, said. The defendants there sent mass e-mail messages that appeared to be authentic communication from the banks, the F.B.I. said.