The latest mass infection to hit the Internet is the Win32/Conficker/Downadup Worm, estimated to have already infected between 500,000 and 8.9 million PCs, depending on whose numbers you believe. This is astounding, considering that the worm exploits a vulnerability in Windows that Microsoft Security Bulletin MS08-067 addressed back in October 2008. Microsoft issued an emergency out-of-cycle patch to address the vulnerability. Windows users who have automatic updates enabled would have received the update so the hole is patched. But there are plenty of people and organizations who, for one reason or another, have automatic updates turned off.
Why any individual PC user would put themself at risk by having automatic updates turned off is beyond me. Organizations are another story; they want to test patches before deployment to ensure they don’t break critical applications or disrupt the network. But in this case, the patch should have been applied without question by every sys admin on the planet. Had this happened, the furor surrounding Conficker.A–the original worm–probably would have died down. Instead, enough sys admins left the hole open that a particularly ferocious variant–Conficker.B–surfaced; it’s the one responsible for the current mass infection.
You can read all about Conficker.B and its blended threat in this post at the Microsoft Malware Protection Center, so I won’t burden you with all the gory details about its blended threat here. I will, however, burden you with my informed opinion: Sometimes you have to heed the warnings and go ahead and patch, regardless of what problems that patch could potentially cause. A network taken down by a malware infection is much worse and potentially more costly to repair than a couple of broken apps here and there.