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Hold your horses

Well, now Microsoft wants us to wait until Patch Tuesday – that'll be the 10th of this month – before we do anything to protect ourselves from this vulnerability. Sophos agrees, at least if you're a business. Here's the latest.

Personally, I'm not going to install the unofficial patch on my work PC – I get the feeling that the IT manager will break my arms – but I have already done so at home. I don't know whether that makes me paranoid or foolhardy.

Here's what my colleagues at Computerworld in the US are advising:

With Microsoft promising a security update "upon completion of [an] investigation" of the WMF security flaw, there's currently no vendor-sanctioned fix for the Windows Metafile vulnerability.

However, there are ways to protect your system and network from potential attack.

"If you are a Windows OneCare user and your current status is green, you are already protected from known malware that uses this vulnerability to attempt to attack systems," according to Microsoft. If not, there are several other defence strategies, including:

1. Un-register the Windows shimgvw.dll file. The command 'regsvr32 -u %windir%system32shimgvw.dll' (without the inverted commas) at the command-line prompt should do this on an individual system. "This workaround is better than just trying to filter files with a WMF extension," according to security firm F-Secure, since some malicious WM files are being disguised with other file extensions.

2. Ilfak Guilfanov ("the main author of Interactive Disassembler Pro and arguably one of the best low-level Windows experts in the world", F-Secure says) has posted a temporary fix at hexblog.com. Security firm iDefense says it tested the patch and verified that it's effective and doesn't seem to include malicious code, but notes that the patch "is still from an independent source, and not the actual vendor, and should be treated as such." SANS also says it has "reverse engineered, reviewed and vetted" the fix. Guilfanov recommends uninstalling his workaround once Microsoft issues an official fix.

3. "Configure Internet Explorer to a HIGH security level," iDefense suggests in a listing of several protection strategies.

4. Block several IP addresses that have been associated with malicious activity in the past, according to Johannes Ullrich with SANS. Details are posted on the SANS Internet Storm Center diary.

"WMF exploitation has rapidly become a major threat, especially as the work week resumes after a long holiday weekend," iDefense spokesman Ken Dunham said in an email advisory. "The situation is rapidly escalating now with hundreds of hostile sites purported, dozens confirmed, and more from public and private data shared to date. Traditionally, any rapid exploitation on a widespread basis within seven days has led to a major meta-event."

For more information on the WMF vulnerability from security vendors and experts, visit:

F-Secure's blog.

SANS Internet Storm Center's diary.

Microsoft's initial security advisory.

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