Any company using Macs in a world full of Windows users needs a virtualization program. You get Windows running on your Mac, so you can make sense of that fussy Web site that won’t behave well enough to run correctly on a Mac, for example. Parallels launched this kind of product, but the much-larger VMWare came out with Fusion about a year later to offer an alternative. Now we hear that Fusion, in any version below 2.0.4, can permit a Windows malware virus to take over a Mac.

Virtualization users run a copy of Microsoft Windows on their Macs. Most use XP, and an independent security company has announced that Fusion permits a Windows bug to take over the Mac OS. VMWare released a 2.0.4 version to fix the hole. This is the opening round of what will probably be a growing problem for Mac owners: viruses built to attack users of things like Fusion and Parallels.

The independent Immunity, Inc. has a video of the kind of hack Fusion permits. It’s enough to make you consider going to Parallels instead of Fusion, if you haven’t selected this kind of tool yet. What’s most important is to keep up with what the virtualization supplier reports about their product. Both of these companies are being proactive about closing these holes. Parallels even includes a one-year-free subscription to its Windows virus-malware protection tool.