A bogus security alert from a "scareware" program. (Image via Microsoft)

A new report from Microsoft cites a big increase in rogue security software -- crafty programs nicknamed "scareware" that warn PC users about purported problems on their machines and try to sell them a fix through bogus security alerts. One popular method of distribution: Fake email messages promising access to explicit celebrity videos, leading to sites that deposit the malicious code.

Seriously, are people still duped by those emails? Apparently so.

"I don’t think I’ve seen a type of threat rise like this for many, many years," writes Vinny Gullotto, general manager of Microsoft's Malware Protection Center, in the company's latest report on Internet security. "Computer users have become increasingly aware of the spread of malicious and potentially unwanted software on the Internet. The bad guys are taking advantage of this by persuading users to install rogue security software that provides little or no real protection, and may actually be malicious in nature."

Once users agree to buy the software, the "bad guys" have their credit card and an inside angle to install even more bad stuff.

The Microsoft report cites a 48 percent increase in rogue security software infections in the second half of last year, based on its analysis of the top 25 malicious software families. Seven of those 25 were connected somehow with rogue software, Gullotto said in an interview.

The trend has gone international -- with rogue security software in languages including Japanese, German, French and Spanish. Microsoft and Washington Attorney General Rob McKenna have filed a series of suits against alleged "scareware" purveyors.

Microsoft's tips for avoiding rogue security software include using up-to-date anti-spyware and anti-malware software from a known vendor; avoiding clicking on ads for unknown software; using a firewall; regularly updating Windows and other programs; and being cautious when clicking on links in email or social networking sites.