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Over the past month we’ve been investigating several high-volume spam runs that sent users to websites compromised with the Black Hole exploit kit. Some of the spam runs that were part of this investigation used the name of Facebook, and US Airways. Other spam runs involved LinkedIn, as well as USPS. The most recent campaign we’ve seen that was part of this wave of attacks used the name of CareerBuilder:

We’ll look at the campaign that used Facebook specifically, but our conclusions about these each of these attacks are broadly similar:

• Phishing messages using the names of various organizations spread via email to targets predominantly in the United States. The content of these phishing e-mails were practically indistinguishable from legitimate messages.
• Links in these messages led to multiple compromised websites that redirected the user to various malicious sites. Collectively, these compromised sites numbered in the thousands.
• Users were eventually directed to sites containing the Black Hole exploit kit.

Now, let’s discuss the spam attack that used Facebook as the lure. This particular spam run consists of a fake friend request sent to the victim, as can be seen below:

The link goes to various compromised web sites. We have identified more than 2,000 distinct URLs used in this attack, distributed over 374 domains. On average, each compromised domain hosted 5 separate malicious landing pages.

As we mentioned earlier, this particular campaign was not the only spam run we investigated. We found clear evidence that all these attacks were linked. In many cases, the same sets of compromised URLs were used by multiple spam runs. This suggests that at least some of the parties responsible for these attacks were identical, if it was not the same group altogether.

The scale of each individual attack is not particularly high as far as spam attacks go. The largest of these attacks were those that used US Airways, which peaked at approximately 1% of all email sent, based on data from Trend Micro product feedback. However, due to their persistence they still pose a serious threat to users.

The goal of these attacks is to install ZeuS variants onto user systems, in order to steal the information of users. We are continuously monitoring for new threats related to these particular threats, and taking all steps to protect Trend Micro users and customers.