"A new malware application named MAC Defender (MacDefender.app) for OS X surfaced a few days ago," warned the MacDefender site. "If you see an application/installer named like this DO NOT DOWNLOAD/INSTALL it. I would never release an application named like this."
The rogueware's name choice was probably a twist on "PC Defender" and "Windows Defender," phrases used in the titles of numerous Windows-based fake AV programs, said James.
Mac users running Safari can prevent MAC Defender from automatically opening after it downloads by unchecking the box marked "Open 'safe' files after downloading" at the bottom of the General tab in the browser's Preferences screen.