Sophos Blocks Windows Shell Attacks

To help safeguard PCs against the Windows Shell -- aka shortcut -- file attack now at large, Sophos on Monday announced the release of Sophos Windows Shortcut Exploit Protection Tool.

The free tool prevents malware from exploiting the Windows Shell vulnerability and warns users when it finds a potential exploit. The tool operates in real time, so users don't have to remember to run it, and intercepts malicious shortcut files both on PC hard drives as well as non-local drives, such as USB drives.

Unlike the Microsoft-recommended workaround and related tool, the Sophos tool won't blank out shortcut file images, turning once colorful and identifiable icons into blank white graphics. Furthermore, Sophos says its tool will work alongside any existing antivirus software.

Malware which exploits the Windows Shell vulnerability first appeared in mid-July, in the form of the Stuxnet worm, which targeted SCADA control systems developed by Siemens, spreading via USB drives. Computers in Iran, more than any other country, appeared to suffer the most infections from Stuxnet.

The shortcut vulnerability is present in Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server R2. Attacks which exploit it are so potent because simply displaying a malicious icon in a Microsoft Explorer or file manager window will trigger the attack. Furthermore, attacks exploiting the vulnerability will work even with AutoRun and AutoPlay disabled.

Since Stuxnet first appeared, four new Windows Shell exploits have been discovered: the Dulkis and Vobfus worms, Chymin keylogging software, as well as a variant of the Zeus financial malware. Thankfully, according to F-Secure, "we don't really expect great success for this particular variant of Zeus," because it relies on social engineering to try and trick users into opening a password-protected zip file and copying the malicious DLL file contained therein to a designated directory.

Still, expect to see more malware gunning for the shortcut vulnerability. According to Graham Cluley, senior technology consultant at Sophos, "details of how to exploit the security hole are now published on the web, meaning it is child's play for other hackers to take advantage and create attacks."

Microsoft has yet to patch the vulnerability.