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Anatomy of a malware scam

The evil genius of XP Antivirus 2008

The warning dialog itself is a GIF image called popup3.gif. Virtually all areas of the page, including popup3.gif, are linked through an on-click event to a function called onloadExecutable(), which looks like this:

function onloadExecutable()
{
dat=new Date(1214372723);
var dlth=dat.getHours()-dat.getUTCHours();
rrc = 1;
location.href="../_download.php?aid=880421&dlth="+dlth;
};

This function does nothing more than trigger a download by setting the location of the browser to a script that initiates a download. The use of this design makes it harder to track down what they are doing since most forensics tools, such as wget, do not execute javascript. The objective, however, is quite clear: you are prompted to download something. The aid parameter is going to be appended to your download name as a version number. The time parameter does not seem to be used at all.

One very interesting behavior of popup3.gif is that the fake close button is actually linked to a special warning. If you click that button, you get the warning in Figure 5.

Figure 5 Closing one warning brings up another

If you click OK in Figure 5 it runs the onloadExecutable() function. If you click cancel or close it throws another warning, shown in Figure 6. That warning will run onloadExecutable() no matter what you do; whether you click the OK button or the red X to close it.

Figure 6 Closing that warning brings up one that gives you no options

Therefore, no matter what you do, you will be prompted to download a file. The file is: http://virus-securityscanner.com/2008/download/XPantivirus2008_v880421.exe. The v880421 part of the file is a fake version number which bubbled all the way from the original page. It does not seem to change very frequently. However, I tried a few hundred different numbers surrounding 880421 and most resulted in a valid download. Disturbingly, they all seem slightly different. It is possible that download.php runs the file through an obfuscator, but more than likely they have a few hundred different obfuscated versions of the same malware sitting on the server.

After downloading the file, I sent it to virustotal.com, a site that scans files on demand using a large number of reputable commercial anti-malware engines. The results varied a little depending on the day I tried it and which version of the file I sent them. For example, on June 24, only GData and Kaspersky detected the current version as malware. A version just a day older was also detected as malicious by AntiVir, eSafe, Sophos, and Webwasher-Gateway. The actual malware contained in the file is the Trojan-Downloader.Win32.FraudLoad.gen downloader trojan

Installing the Malware

The malware is actually quite well written, looking very professional. The installer starts out with a notification shown in Figure 7. It includes what appears to be a Windows compatibility logo, fake of course, and has a link to the terms and conditions.

Figure 7 The installer looks very professional

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