Trojan steals session IDs, bypasses logout requests

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A new banking trojan targeting U.S. customers has the ability to keep online account sessions open after customers believe they have logged off, enabling criminals to surreptitiously steal money, according to researchers at web security firm Trusteer.

Eastern European cybercrooks are using the trojan, dubbed “OddJob” by researchers, to attack banking customers in the United States, Poland and Denmark, Amit Klein, CTO of Trusteer, told SCMagazineUS.com on Tuesday.

The malware is designed to hijack a victim's online banking session using their session ID tokens – unique identifiers assigned to a user who has logged into a website, he said. But perhaps the most dangerous aspect of  OddJob is that it can bypass a user's logout request, allowing fraudsters to remain connected even after a user believes they have successfully logged out. 

“When a user tires to logout of the session, they are unable to do so, extending the longevity of the session considerably and allowing [the attackers] to conduct fraud at their convenience,” Klein said.

Trusteer researchers have been monitoring OddJob for several months but have been tight lipped about their discovery due to ongoing investigations by law enforcement agencies, said Klein, who would not reveal which banks have been targeted.

The masterminds have made numerous changes to the trojan's functionality and command-and-control (C&C) infrastructure over the past several weeks, leading researchers to believe it is a work in progress, he added.

While OddJob is not as prevalent as other banking trojans like Zeus or SpyEye, Trusteer researchers believe it will become a greater threat as crooks continue to refine it.

Depending on its configuration, OddJob can perform a variety of actions on targeted websites, such as logging web requests, capturing full pages, terminating connections and injecting data into web pages. All stolen requests and pages are instantaneously sent to C&C servers, allowing attackers to hijack users' sessions in real time without victims realizing anything is amiss.

“The most important difference from conventional hacking is that the fraudsters do not need to log into the online banking computers – they simply ride on the existing and authenticated session, much as a child might slip in unnoticed through a turnstile at a sports event [or] train station,” Klein wrote in a blog post Tuesday.

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