The program is embedded inside an MP3 music file, according to Intego, a maker of security and privacy software for Apple.
Paris-based Intego said that the program it received doesn't cause any destruction when activated but warned that the code could be easily modified to cause damage, such as to delete files. The company said the program, which opens a secret door for hackers to exploit at a later time, isn’t circulating on the Internet.
"We take this first Trojan very seriously," Intego CEO Laurent Marteau said. "This is very easy to modify and create a different version of the same problem."
With a mercurial rise in digital music, driven by its popular iTunes music store and iPod portable players, virus writers may be focusing on music files to spread mayhem.
Double-clicking on the attached MP3 file launches the iTunes music program and simultaneously spawns the Trojan program in the background, Marteau said, adding that it does not appear to be destructive except under computer certain settings.
With a 5 percent share of the personal computer market, the Mac is not the most attractive target to virus writers. Only 24 of the 88,000 malicious programs blocked by Network Associates Inc.'s McAfee antivirus software were written for Mac operating systems. Most are more than 10 years old, and none ever got very far.
With that low risk, few Mac users run antivirus software.
Apple's operating system, Mac OS X, was released in early 2001, while Apple's iTunes music service was introduced in late 2003.