Between June 24 – 27, cyber criminals used Facebook spam messages to distribute malware. For 48 hours the virus hijacked user accounts to perform various operations, such as giving likes and sharing unwanted content.
A Kaspersky Lab security expert found out that the malware campaign was spreading among Facebook accounts in the form of a spam message received from a friend, informing users about being mentioned in a comment. Once accessed by a user, the link would start the first phase of the two-stage attack, which would secretly download a trojan on the victim’s PC.
In the second stage, the trojan would download and secretly install an extension in the user’s Chrome browser, if found on the infected system. The Chrome extension would wait until the victim tried to access Facebook again, asking him to re-authenticate. This is the moment when the extension would log the user’s Facebook username and password and send them to the hacker’s server.
After that the hacker would then take advantage of these credentials and instruct these accounts to give likes and shares to desired content. At the same time, he will be spamming the infected account’s friends to spread the malware further.
In other words, the hacker behind the malware campaign was most likely selling Facebook Likes and Shares via his botnet of infected devices. Due to the trojan’s source code, the malware was only effective when users viewed the spam messages from Windows computers.
According to Kaspersky Lab, the malware tried to protect itself by blacklisting the homepages of several security software vendors.
“Two aspects of this attack stand out. Firstly, the delivery of the malware was extremely efficient, reaching thousands of users in only 48 hours. Secondly, the response from consumers and the media was almost as fast. Their reaction raised awareness of the campaign and drove prompt action and investigation by the providers concerned,” explained Ido Naor from Kaspersky Lab.
Being alerted, the engineers from Facebook moved on to block the techniques used by the malware to spread. Google has also removed the rogue extension from its Chrome Web Store.
The Kaspersky’s data shows that this malware campaign made the most victims in countries such as Brazil, Portugal, Tunisia, Venezuela, Peru, Colombia, Mexico, Ecuador, Israel, Germany, Poland, and Greece.