Since time immemorial, we always believed that Mac OS based computers were free from malware and other such nasty stuff. In fact, the no virus/malware on Macs used to be touted a feature and one of the biggest reasons to buy a Mac.
No longer safe?
The fake MacDefender uses the name of a legit anti-virus developer and looks quite convincing by copying the looks of the original software. Once installed, it starts finding non-existant viruses and starts loading up pornography on the user’s computer. The reason it does so is to force the users into parting with their credit card information, which the malware states is necessary to remove the viruses and spam messages.
Those who are infected can follow the steps given at The Next Web. But those who aren’t infected and want to stay safe can uncheck the “open 'safe' files after downloading” option in the Safari web browser as well as use a little common sense.