The Downadup worm may have already created havoc with the estimated nine million PCs it's infected, but one security expert warns the worm is only dormant, perhaps to be unleashed at a later date with an even greater vengeance.

Jason Miller, manager of security and data at St. Paul, Minn.-based security technology vendor Shavlik Technologies LLC, said Downadup (also referred to as Conficker) may well be undergoing a test run, during which its makers are learning of what works best.

If that's the case, there's a more malicious version in store for everyone, predicts Miller. "It's a blessing in disguise," he said, and organizations and individual users can take advantage of this lull to ensure their systems are secure. "This worm is not going to go away."

Nor does Miller think the estimate of infected PCs at nine million by Finland-based security firm F-Secure Corp. is a mere scare tactic. "Whoever wrote this virus has a lot of information tucked in their head," he said, referring to the sophisticated techniques employed by Downadup.

There's a complexity with this one, said Miller, that's replacing a virus or worm's usual one-dimensional approach, which is either to set up spam or download an application on a victim PC. Upon closer inspection, Downadup assumes a multi-vector strategy employing brand new techniques not previously seen "and they're pretty scary," he said.

Among those, the worm takes advantage of a previous file-sharing vulnerability in Microsoft Windows Server, and also proliferates itself by infecting USB devices.

Users of Windows 2000, Windows XP and Windows Server 2003 systems are most at risk, according to Microsoft Corp., which last October released a patch, MS08-067, intended to protect systems from Downadup, and has also advised users to download the Malicious Software Removal Tool (MSRT), updated last week to detect and remove the worm.

Organizations should scour their network for all physical and virtual machines that exist, such as the one "buried in the basement somewhere," said Miller. "Look for those systems that you can't find. Don't worry about the main PCs and the servers on the floor. All it takes is one."

Miller also suggested stopping Downadup by disabling ports 135 and 443. However, he cautioned, that is a band-aid approach that risks interrupting file-sharing, thereby disrupting the internal functioning of Windows and other systems that rely on those ports. "If you have to and you're in a crunch, I would say do it, but just be advised it will break functionality of products," he said.

Hardening passwords and enforcing policies for password creation, said Miller, is recommended, so "you can't let me have my password as 'Miller' when my username is 'Jason.'"

It's also a good idea to disable Autoplay and Autorun in Windows so those functions don't automatically run when a USB device is plugged in, said Miller.

Markham, Ont.-based IT security technology vendor Panda Software Canada posted on its blog, a little more than a week ago, similar suggestions to help organizations prevent attack and cleanse their systems of Downadup infections. The worm "means business so be careful out there," the blog entry read.