If a user downloads a MacDefender variant using Safari, iChat or Mail -- the Mac's native email client -- Snow Leopard posts an on-screen notice that reads, "filename will damage your computer. You should move it to the Trash."

The default button of "Move to Trash" will dump the malware into the bin.

A week ago, Apple posed by what security experts call "scareware" or "rogueware," and promised to issue an update to detect and delete such software.

The terms refer to bogus security programs that claim a personal computer is heavily infected with worms, viruses and other malware. Once installed, scareware nags users with pervasive pop-ups and fake alerts until they fork over a fee to purchase the worthless program. MacDefender demands $60 to $80 as its "registration" fee.

French security company Intego , the first piece of professional-looking scareware to target Macs, in early May. Since then, several variants have appeared, including one named MacGuard that installed .