The FBI is cracking down on an international identity theft operation that involves the trading of social security numbers; the sale of stolen credit card account information; and phishing, the practice of using e-mail to trick consumers into handing over personal information, authorities said. Called Operation Cardkeeper, the investigation has brought about the arrests of more than a dozen people in the United States and other countries who are members of online communities that specialize in "carding," the trafficking of stolen identities and credit card and bank account information.