Here at SophosLabs we've been working out the best way to protect computer users against the zero-day flaw that has hit all versions of Windows.As you have probably heard by now, there's a vulnerability, known as the "shortcut exploit," that affects the way Microsoft Windows handles .LNK shortcut files. If Windows tries to display the icon of an exploited shortcut file, it can run the malicious code pointed to by the shortcut -- without any user interaction.

One of the ways we have seen this problem exploited is via malware infections on USB sticks, which are capable of running viral code even if AutoPlay and AutoRun are disabled.

Microsoft issued an emergency "workaround," but unfortunately it blanks out your shortcut icons on your desktop in a rather ugly, scary manner -- probably not something you want to roll out across your entire organization.

Our Sophos antivirus product protects our customers from the shortcut exploit, but to help others we've produced a free tool that installs a new icon handler for Windows shortcuts.

Whenever Windows tries to display an icon corresponding to a Windows shortcut, the new icon handler will intercept this request and validate the shortcut. If the shortcut does not contain the exploit, then control will be given back to Windows.

But if the shortcut does contain an exploit, then a message is displayed to the user and extraction of the dangerous icon is blocked.

What's really nice is that it doesn't matter which antivirus software you're using: You can still install this free tool from Sophos, and it will work alongside your existing antivirus.

Hopefully soon Microsoft will release a proper patch to protect against the shortcut vulnerability, and then you can simply uninstall the Sophos tool. But in the meantime, this is pretty nifty.

You can download the free tool here.

Graham Cluley is senior technology consultant at Sophos, and has been working in the computer security field since the early 1990s. When he's not updating his award-winning other blog on the Sophos website, you can find him on Twitter at @gcluley. Special to Dark Reading.