The image above is a screencap of the program Mac Defender. The program runs a “scan” of Mac computers, then tell users that–surprise!–their Mac is crawling with malware. that’s quite alright though, because if the user just enters their credit card info, the registered version of Mac Defender will save the day, ridding the Mac of those dastardly viruses.
Of course, Mac Defender’s not a real anti-virus program. It’s an example of rogue security software, malicious programs that claim to be protecting computers, all the way trying to bilk users out of credit card info, and in some cases hijacking their browsers and making the computers generally unusable.