The scammers use variations of the Zeus and SpyEye Trojans to infiltrate targeted corporate accounts with the specific goal of initiating Sepa Credit Transfers to mules across the EU

The malicious "webinjects" targetted two German banks with a specially crafted JavaScript payload deployed to about a dozen of their online banking customers which have Sepa as an option, says McAfee. The campaigns are hard to detect because they infect only a few dozen customers and take advantage of the automated channels developed by banks to distribute Sepa payments.

The system, which is being run out of Moscow, is hard-coded to allow up to a maximum of €100,000 for a single Sepa transaction and a minimum of €1,000.

"For one of the financial institutions targeted, we estimated from the log files we retrieved that €61,000 in attempted Sepa transactions were made to mule accounts," says McAfee. "Some of the accounts had more than €50,000 as the standing account balances."