The FBI’s Cyber Division is looking into more than 400 reported cases of corporate account takeovers, Cyber Division Assistant Director Gordon Snow told the House Financial Services Committee’s Subcommittee on Financial Institutions and Consumer Credit in Sep. 14 testimony.

The cases involve unauthorized ACH and wire transfers from the bank accounts of U.S. businesses, which typically began with phishing e-mails sent to employees within targeted companies, who unknowingly installed malware by opening attachments or links, Snow said in the testimony.

Criminals stole approximately $85 million from their victims, but attempted theft of more than $255 million, the FBI said.

The malware usually contains a keylogging program that allows criminals to capture sensitive online banking information and steal funds, which is often transferred overseas; this type of crime has affected small and medium-sized businesses, local governments, school districts and health care service providers, the FBI said.

“Malicious cyber incidents are costly and inconvenient to financial institutions and their customers, and although most businesses take action to recover quickly, limit impact to customers and ensure long-term operational viability, the increasing sophistication of cyber criminals will no doubt lead to an escalation in cyber crime,” Snow said in the testimony.

The testimony also warned of growing third-party payment processor breaches, ATM skimming, point of sale schemes and mobile banking exploitation. Newer threats involve sophisticated ATM skimming devices, such as Bluetooth-enabled wireless skimmers that were found at a number of gas stations in the Denver area, and malicious “tweets,” which criminals are sending through iPhone Twitter apps and contain links to malware.

The recent phishing crimes follow a string of widely publicized attacks in 2011, including the e-mail address security breach at marketing firm Epsilon and a skimming scam that targeted national craft chain Michaels.