Exploit:Java/CVE-2010-0840.BC

Exploit:Java/CVE-2010-0840.BC is the detection for a malicious Java applet trojan that exploits a vulnerability described in CVE-2010-0840. Successful exploitation may lead to the downloading and execution of arbitrary files under the user's security context.

Exploit:Java/CVE-2010-0840.BC is an obfuscated Java applet trojan 8314 bytes in size. The applet is referenced by the name "messenger" and is distributed as a part of a Java archive (.jar) package 7517 bytes in size. In the wild, we have observed the package being detected with names related to the Internet Explorer cache files, however, the name is irrelevant for the trojan's functionality and may vary. The package also contains the following Java class files:

 

 

When executed, the trojan attempts to exploit a vulnerability described in CVE-2010-0840 to gain the user's account security privileges on the targeted computer. The vulnerability affects Java Runtime Environment (JRE) up to version 6 update 18.

 

If successful, the trojan downloads, writes and executes an arbitrary file, stored within the Windows 'temp' folder. The arbitrary file is referred by a URL string stored in a parameter "id", which is specified inside the applet HTML file. The downloaded file is executed under the user's security context. The applet consists of the following member functions:

 

 

The function _75e7ec88cff9b65a6a84345500ef2d94 and __e are used for decrypting of encrypted strings inside the applet. When the applet is opened within a browser, a "constructor" of the applet, the 'messenger' function is executed first. If the exploit is successful, the 'start' function facilitates the downloading and execution of an arbitrary file. The other class files in the .jar package serve to obfuscate the Java applet and the strings within.

It is not uncommon for antivirus software to detect malicious Java applets in a web browser's cache. It doesn’t necessarily mean that the system is compromised. Most of the time it reflects the fact that at some stage, a webpage with a malicious applet had been visited and cached internally. To thwart such a notification it is often enough to purge the cache using a web browser's configurable security options.

 

Analysis by Oleg Petrovsky