We've previously warned about the rising number of scareware threats attempting to scam Internet users. Now Microsoft and the state of Washington are gnashing their legal teeth. Will it work?

Last week I'm surfing the Net using Firefox on a Mac running Leopard 10.5 and I get a pop-up window telling me that my system is in critical need of a Registry cleansing. Oh, really? Too bad OS X doesn't have a registry.

Turns out I wasn't the only one. Now, I didn't take note of what company was behind the pop-up window that tried to scam me. But the joint Washington Attorney General and Microsoft civil lawsuit announced today is against James Reed McCreary IV of The Woodlands, Texas, and two companies he runs -- Branch Software and Alpha Red -- for allegedly selling scareware known as Registry Cleaner XP.

From today's news story by Thomas Claburn:

Registry Cleaner XP qualifies as scareware because it allegedly identifies nonexistent security vulnerabilities in order to dupe victims into buying fraudulent security mitigation services. Scareware is generally regarded to be a form of spyware.

By misusing the Windows Messenger Service, a protocol designed to allow administrators to send messages over a network, McCreary and his companies have been delivering pop-up ads to computer users who have not chosen to disable such messages, according to the legal complaint.

I'll state the obvious: this stuff is scourge. And I hope they're able to use anti-spyware legislation to levy heavy fines against any company using these scare tactics to steal from unwitting victims. While the readers of InformationWeek can probably easily spot these scams, there are millions of Internet users who can't.

Take a look at an earlier post of mine that details the recent spike, and profitability, in scareware scams.