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In this paper, we have taken a behind-the-scenes look at malicious web servers that launch drive-by-downloads. We analyzed specific aspects of several web exploitation kits that allowed us to reexamine several questions that we were unable to answer with our previous study on malicious web servers. The web exploitation kits provided us with valuable insight on how malicious web servers operate. (For comprehensive analysis of MPack and WebAttacker we refer to existing reports , .) There are several conclusions we draw as a result of our analysis with respect to future studies and client honeypot technology:
First, the appearance of web exploitation kits have a positive effect on identification of malicious web servers. Since they are tools that can be relatively easily obtained and deployed, it has a homogenizing effect on the malicious web server landscape (4.24% of the URLs encountered in our KYE study used MPack; WebAttacker apparently composed 32% of reported exploits in June 2006 ). Characteristics about the tool and the malicious content it serves can currently be identified and matched upon. We demonstrated that we can easily identify MPack servers using our low interaction client honeypot HoneyC as well as behavioral attack signatures. Whether attackers will invest energy and resources to “fix” these weaknesses remains to be seen.
Exploit servers are high value identification targets. Because they are used for numerous front-end pages, it is not likely that they will disappear. Rather, it is suspected that attackers will frequently update these exploit servers, which allows security researchers to observe the latest attacks. All web exploitation kits reviewed allow attackers to purchase upgrades, which will likely appear on the same machines.
On the other hand, the web exploitation kit MPack showed us that our identification of malicious web servers with high interaction client honeypot, such as Capture-HPC, has some limitations. First, the IP tracking functionality throws a wrench in the works of client honeypots and is likely to result in many false negatives if not addressed appropriately. A study into the magnitude of this technique and adjustments into the client honeypot approach are needed. It is likely that distributed client honeypots will become a necessity in the near future. Second, geolocation-dependent triggering is something we had not yet considered. Depending on what countries are prime targets, it might also result in a large number of false negatives. A comparitive study finding malicious servers using client honeypots in different physical locations will be necessary to assess the magnitude of the problem.
The web exploitation kits also showed us that other client applications/plug-ins are targeted. This is bad news for the end user whose many client vulnerabilities are now being actively attacked and comparing supported attacks of WebAttacker, MPack and IcePack seems to indicate a trend. As a result, client honeypots would require more complex configurations in search of malicious servers. In our previous study, we likely missed numerous attacks. With the insight provided by web exploitation kits, we are planning to address these gaps in future studies to come.