Here’s something for those of you responsible for keeping your family computers up to date with patches, virus scans and that sort of stuff.

There’s a fast-moving worm out there infecting computers across the world, using a vulnerability found in Microsoft Windows.Microsoft actually released a patch in October that’ll protect your computer. But experts estimate that 30 percent of the computers attached to the Internet are still vulnerable. Because people aren’t installing the patch.

Worms like Conficker not only ricochet around the Internet at lightning speed, they harness infected computers into unified systems called botnets, which can then accept programming instructions from their clandestine masters. “If you’re looking for a digital Pearl Harbor, we now have the Japanese ships steaming toward us on the horizon,” said Rick Wesson, chief executive of Support Intelligence, a computer security consulting firm based in San Francisco.

The funny, or scary, thing about this particular virus is that security experts still aren’t sure what it’s there for and what it might do.

Computer security researchers expect that within days or weeks the bot-herder who controls the programs will send out commands to force the botnet to perform some as yet unknown illegal activity.

Several computer security firms said that although Conficker appeared to have been written from scratch, it had parallels to the work of a suspected Eastern European criminal gang that has profited by sending programs known as “scareware” to personal computers that seem to warn users of an infection and ask for credit card numbers to pay for bogus antivirus software that actually further infects their computer.