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A web exploitation kit allows an attacker to gain control of a client machine when it visits a malicious web page. The steps that lead to successful exploitation are shown in Figures 1 and 2 show the steps that are usually taken by these drive-by-downloads . First, a user visits a web page that hosts a web exploitation kit. Following the client's request, the web server might implement some server side logic that assesses from what country the request is coming, what browser is being used, etc. and then returns the attack code as part of the response. The attack code attacks the client, and if successful, executes a downloader component without the user's consent or notice (Step 1). The downloader in turn will make a follow-on request to download and execute a piece of malware from a URL specified by the attacker (Step 2). Alternatively, the step can be skipped and the malware delivered with the initial attack code making Step 2 unnecessary. At that point, the attacker has complete control of the client machine and can steal sensitive information, such as credit card numbers or account credentials, join the client machine in a botnet, use social engineering to entice the user to purchase bogus products online, etc. The user did not notice that he was just successfully attacked as all steps are happening in the background. As such, drive-by-downloads is a popular technique in the attacker's arsenal.
Figure 1 - Client-Side Attack - Step 1
Figure 2 - Client-Side Attack - Step 2
WebAttacker is one of the first web exploitation kits that appeared in early 2006. It was sold on Russian web sites for about $15 . MPack, a more sophisticated web exploitation kit, was developed shortly after by three Russian programmers who call themselves the “Dream Coders Team” , and was initially released in June 2006. The tool is sold via the underground market for approximately $700 to $1000 and according to VeriSign/iDefense , it has been responsible for thousands of infections. IcePack was first reported in July 2007 ,  and is quite similar to MPack. It has been developed by another group, the IDT group, with a purchase price of $400. Since August 2007 even Chinese localizations of the MPack/IcePack toolkits are available .
Under the hood, these web exploitation kits are quite simple. WebAttacker consists of a Perl and some PHP scripts. MPack/IcePack consists of several PHP scripts and a downloader creator that allows the user to create custom downloaders, programs designed to retrieve and install the actual malware. The use of the downloader frees the attacker from any size limits posed by the payload buffer and potentially provides some encryption routines to evade intrusion detection systems. Our test installation of MPack was as easy as unpacking the MPack archive into a directory, editing a simple configuration file and placing the downloader into the directory. The provided documentation and sample configuration assisted us in our efforts. Once the web exploitation kit is installed, attacks are live and accessible on the web server under a specific URL, and the attacker's only remaining task is to entice users to visit this URL.
Once a kit is set up, the application can provide the attacker with information about the progress of its attacks via a password protected administrative/statistics page. The MPack administrative interface is shown in Figure 3 . It primarily contains information on the success rate of the various attacks and information about the location of the attacked clients. Similar administrative interfaces exist for WebAttacker and IcePack. We will review the administrative interface of MPack in more detail below.