Countries in Latin America have been the primary targets in this campaign, researchers say.
Edwin Vargas, 42, was arrested on Tuesday for allegedly buying email login credentials and cracking fellow officers' email accounts.
Over the past three days, security companies announced acquisitions.
Users have been urged to change their passwords as a precaution.
The number of fraud complaints lodged with the Internet Crime Complaint Center actually fell in 2012, but the amount of alleged losses to victims rose.
The weakness allows for an intruder to quietly have access to any files stored on the server.
Adrian-Tiberiu Oprea, a Romanian man, admitted that he helped steal payment card data from hundreds of U.S.-based point-of-sale (POS) systems at the sandwich chain.
Mapco disclosed this week that hackers compromised its payment card processing systems to steal credit and debit card information belonging to an unknown number of customers.
Intel-owned McAfee has acquired next-generation firewall maker Stonesoft for $389 million, the companies announced Monday.
The microblogging service told news organizations that they will continue to be "high value targets to hackers."
