Kaspersky researchers have discovered two new Android malware modifications that, when combined, can steal cookies collected by the browser and app of popular social networking sites and then allow the thieves to discreetly gain control of the victim's account in order to send ill-intentioned content. 

Cookies are small pieces of data collected by websites to track users' activity online, in an effort to create personalized experiences in the future. While they're often perceived as a harmless nuisance, they can, in the wrong hands, pose a security risk. That's because, when websites store these cookies, they use a unique session ID that identifies the user in the future without requiring a password or login. Once in possession of a user's ID, tricksters can fool the websites into thinking they are in fact that person and take control of their account.

That's exactly what these cookie thieves did by developing two Trojans with similar coding, controlled by the same command and control (C&C) server.

The first Trojan acquires root rights on the victim's device, which allows the thieves to transfer Facebook's cookies to their own servers.

However, oftentimes, simply having the ID number isn't enough to take control of an account. Some websites have security measures in place that prevent suspicious log-in attempts-say, for example, a user previously active in Chicago attempts to log in from Bali just a few minutes later.

That's where the second Trojan comes in. This malicious app can run a proxy server on a victim's device to bypass security measures, gaining access without arousing suspicion. From there, the criminals can pose as the victim and take control of their social networking account to distribute undesirable content. 

While the ultimate aim of the cookie thieves remains unknown, a page uncovered on the same C&C server could provide a hint: the page advertises services for distributing spam on social networks and messengers. In other words, the thieves may be looking for account access as a way to launch widespread spam and phishing attacks.

"By combining two attacks, the cookie thieves have discovered a way to gain control over their victims' accounts without arousing suspicions," Igor Golovin, malware analyst at Kaspersky. "While this is a relatively new threat-so far, only about 1000 individuals have been targeted-that number is growing and will most likely continue to do so, particularly since it's so hard for websites to detect. Even though we typically don't pay attention to cookies when we're surfing the web, they're still another means of processing our personal information, and anytime data about us is collected online, we need to pay attention."

Read more about the Cookiethief on Securelist.

Here's how you can prevent yourself from becoming a victim of cookie theft:

• Block third-party cookie access on your phone's web browser and only let your data be saved until you quit the browser
• Periodically clear your cookies
• Use a reliable security solution like Kaspersky Security Cloud that includes a Private Browsing feature, which prevents websites from collecting information about your activity online