The Department of Homeland Security is warning of an imminent attack -- on your personal computer or your server at work. There is a patch available, but if enough users don't install it, the result could be the fastest-spreading destruction in Internet history.

The problem lies with a security hole in the most popular versions of Microsoft's (NASDAQ:MSFT) ubiquitous Windows operating system. Joshua Brown, chief security goon for The Motley Fool, says this one is particularly dangerous because it would give a hacker, in essence, "full control over a compromised system."

Adding to the problem is the breadth of systems affected: Windows NT 4.0, Windows NT 4.0 Terminal Services Edition, Windows 2000, Windows XP, and Windows Server 2003.

Aside from the fact that Windows XP has been "shipping on essentially every home computer sold in the last 12-18 months," Brown says, the vulnerability also affects every server running Microsoft operating systems -- "which is the sizeable majority of all server systems in production."

Aside from other destruction, all of this means hackers could release a virus or worm that has the potential to spread faster than the recent "CodeRed" worm.

Homeland Security officials expect a wide-scale attack any day now because of "an Internet-wide increase in scanning for vulnerable computers over the past several days." If you're a computer owner or administrator running the software in question, you can update your Windows operating system by visiting this link. Doing so will eliminate this particular vulnerability.