W32 Silon Trojan bypasses security tokens and banking card readers to commit online financial fraud

(13/11/2009)

The new Trojan called W32.Silon bypasses security tokens, banking card readers and uses a two pronged payload to steal login information and commit online financial fraud. W32.Silon is new malware variant that intercepts Internet Explorer web browser sessions, and has been associated with fraud incidents at several large banks.

The Trusteer Rapport browser security service has blocked repeated attempts in-the-wild by the W32.Silon Trojan to compromise consumer internet banking accounts. Findings gathered from a sample of the new malware are available in a report that explains its functionality, as well as how to detect and remove W32.Silon.

Trusteer retrieved and analyzed a sample of this two headed Trojan which is designed to steal generic login information and commit bank-specific fraud. To steal user credentials, W32.Silon performs its initial attack when a user initiates a web login session and enters their username and password. The malware intercepts the login POST request, encrypts the requested data, and sends it to a command & control (C&C) server.

When it targets users of online banking applications that are protected by transaction authentication devices such as tokens or banking card readers, W32.Silon waits until the user has logged on and then injects dynamic html code into the login flow between the user and the bank's web server. First, the malware presents authentic looking web pages that appear to be from the bank asking the user to employ their transaction authentication device. Next, the user is asked to enter information from the device into the webpage. This information is then used by the criminals to execute fraudulent transactions on behalf of the user.

"This new Trojan illustrates how advanced malware writers have become in their ability to dynamically execute multiple, bank-specific attacks with a single piece of software," said Amit Klein, CTO and chief researcher at Trusteer. "The level of sophistication built-into W32.Silon is concerning, as is its focus on circumventing strong authentication systems like card and PIN readers. We have put all of our banking customers on alert, and are attempting to get the word out with this advisory."

Related topics:  Authentication and identity management   Hacking and intrusion prevention   Internet and Web security   Virus, Worm, Email security, spyware and malware 

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