An online scam scheme sends junk email messages telling people that a hotel has mistakenly charged their credit card with a wrong payment. The result of being victimized is an infected PC.

According to reports the messages appeared on the net in recent days and so far there are hundreds of versions already. The main theme is: A hotel wrongly charged a credit card number and the victim is supposed to fill out an attached form to process the refund.

"Please see the attached form. You need to fill it out and contact your bank for return of funds," read one such message, titled "Hotel Breakers Palm Beach made wrong transaction."

If an unwitting person presses the attachment their computer will be infected with a malicious Trojan horse program that installs fake antivirus software on the victim's computer, according to Gary Warner, director of research in computer forensics at the University of Alabama at Birmingham, who blogged about the spam messages Wednesday.

Consumers who aren't sure whether these messages are legitimate should use Google to find the company's website and then call them, security experts advise.