Once run, the dropper downloads the second-stage backdoor and opens a Chinese-language PDF. F-Secure said that the PDF was another sleight-of-hand trick: "[The dropper component] drops a PDF file in the /tmp folder, then opens it to distract the user from noticing any other activity occurring," the company said in a of the attack.

Both Sophos and F-Secure noted that the malware doesn't work reliably, and currently can't connect to the command-and-control (C&C) server because the latter isn't fully functional.

Mac malware is typically crude in comparison with what targets Windows PCs.

Because the C&C server is not yet operational and since it found samples of the Trojans on VirusTotal -- a free service that runs malware against a host of antivirus engines -- F-Secure speculated that the malware is still in the testing phase.

Although Apple's Mac OS X includes a bare-bones antivirus detector, it has not been updated to detect the just-noticed Trojan dropper or backdoor. Checks of several Computerworld Macs running Lion, for instance, found that Apple last updated its detector on Aug. 9.