Online bank punters tricked into approving theft of their OWN CASH

Man-in-browser Trojan attack discovered

Security researchers have discovered a malware-based attack against the chipTAN system used by bank customers in Germany to authorise transactions online.

The chipTAN system involves the use of a card reader into which a chip-n-PIN bank card is inserted, which generates a transaction authentication number (TAN) used to green-light a transfer via the bank's website*.

The Tatanga attack bypasses chipTAN systems by fooling users of malware-infected machines into authorising fraudulent transfers from their accounts, security biz Trusteer warns.

The Tatanga banking Trojan initially injects code into a trusted online banking web page to fool the user into believing that the bank has requested the punter performs a chipTAN "test". The user is then asked to generate a TAN for the "test" transaction and enter the authorisation code into an HTML page mimicking the look and feel of the bank's website.

In reality the code is being used to authorise a fraudulent transfer from the user's online banking account to that of the miscreants.

The malware also covers its tracks; it is designed to replace the user's transaction history and balance details to hide the fraudulent transfer from the victim.

"ChipTAN systems are considered fairly secure, because the generated TAN takes into account both transaction details and the bank issued chip-and-pin card," said Trusteer’s CTO Amit Klein. "However, this attack demonstrates that by using man-in-the-browser social engineering techniques, financial malware can circumvent chipTAN security. Implementing endpoint protection against advanced malware like Tatanga, ZeuS and others is the only way to make sure that the integrity of second factor security measures like chipTAN are not compromised."

More details on the Tatanga attack can be found in a blog post by Trusteer here. ®

* It is a process similar to the systems in card readers issued by UK banks. By contrast, ChipTAN uses an optical reader which must be used by the customer to scan a "flicker code" shown on-screen on the bank's website whenever a transaction is requested.

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