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Malicious Content Injection

In Section 4, we showed that exposure to web-malware is not strongly tied to a particular browsing habit. Our assertion is that this is due, in part, to the fact that drive-by downloads are triggered by visiting staging sites that are not necessarily of malicious intent but have content that lures the visitor into the malware distribution network.

In this section, we validate this conjecture by studying the properties of the web sites that participate in the malware delivery trees. As discussed in Section 2, attackers use a number of techniques to control the content of benign web sites and turn them into nodes in the malware distribution networks. These techniques can be divided into two categories: web server compromise and third party contributed content (e.g., blog posts). Unfortunately, it is generally difficult to determine the exact contribution of either category. In fact, in some cases even manual inspection of the content of each web site may not lead to conclusive evidence regarding the manner in which the malicious content was injected into the web site. Therefore, in this section we provide insights into some features of these web sites that may explain their presence in the malware delivery trees. We only focus on the features that we can determine in an automated fashion. Specifically, where possible, we first inspect the version of the software running on the web server for each landing site. Additionally, we explore one important angle that we discovered which contributes significantly to the distribution of web malware--namely, drive-by downloads via Ads.

Niels Provos 2008-05-13