News, blogs, opinions — Twitter is one of the most popular social networks for spreading ideas. It has revolutionized the way millions of people consume news. With 288 million active users, Twitter is the world’s fourth-largest social network, so it’s no surprise that Twitter malware attacks are on the rise.

IBM’s Tanya Shafir has recently identified an active configuration of financial malware targeting Twitter users. The malware launches a Man in the Browser (MitB) attack through the browser of infected PCs, gaining access to the victim’s Twitter account to create malicious tweets. The malware, which has been used to gain access to users’ credentials and target their financial transactions, now has a new goal: to spread malware using the online social networking service. At this time, the attack is targeting the Dutch market. But because Twitter is used by millions around the world, this type of attack can be used to target any market and any industry.

Tweeters Beware

The attack is carried out by injecting Javascript code into the victim’s Twitter account page. The malware collects the user’s authentication token, which enables it to make authorized calls to Twitter’s APIs, and then posts new, malicious tweets on behalf of the victim. Here is an excerpt from the injected Javascript code:

Here are some examples of the tweets posted by the malware from victims’ accounts (tweets containing explicit content were omitted from this blog post):

• Original text (in Dutch): “Onze nieuwe koning Willem gaat nog meer verdienen dan beatrix. check zijn salaris”
  • (English translation: “Our new King William will earn even more than Beatrix. Check his salary”)
• “Beyonce valt tijdens het concert van de superbowl, zeer funny!!!!”
  • (“Beyonce falls during the Super Bowl concert, very funny!!!!”)
• “topman [Dutch Bank] gaat ervandoor met onze miljoenen!! De minister heeft weer het nakijken… zie”
  • (“CEO of [Dutch Bank] is off with our millions!! The minister is inspecting again… see.” N.B., we have removed the bank’s name from the original tweet)

The tweets include the following malicious links (all appear to be inactive at the moment):

• hXXp://yix.be/b18e9
• hXXp://yix.be/11efb
• hXXp://ow.ly/hr6a6
• hXXp://01.nl/rohvj9

IBM researchers found these texts in multiple Twitter posts indicating that this attack has been successful at ensnaring victims.

Protecting Users and Enterprise Endpoints from Twitter Malware

This attack is particularly difficult to defend against because it uses a new, sophisticated approach to spear phishing. Twitter users follow accounts that they trust. Because this Twitter malware creates malicious tweets and sends them through a compromised account of a trusted person or organization, followers assume the tweets are genuine. The fact that the tweets include shortened URLs is not concerning: Twitter limits the number of characters in a message, so followers expect to get interesting news bits in the form of a short text message and a shortened URL. However, a shortened URL can be used to disguise the underlying address so that followers have no way of knowing if the link is suspicious.

While Trusteer did not inspect the URLs posted, it is quite possible that these URLs lead to malicious Web pages. If so, when the browser renders the Web page’s content, an exploit can silently download the malware to the user’s endpoint (a drive-by download).

This type of attack increases the need for enterprise exploit prevention technology. By blocking the exploitation of vulnerable endpoint user applications such as browsers and preventing the malware download, exploit prevention technology stops the attack and prevents the malware from spreading and infecting more users. External sources like Web content and email attachments, which can include a hidden exploit in the form of embedded code, should never be trusted. Such content should only be opened while monitoring the application state to ensure it is operating legitimately.

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