Though largely immune to the malware issues plaguing Windows users, users of Apple's operating system may soon be joining their Windows counterparts.

Anti-virus vendor Sophos Labs reports the emergence of a backdoor Trojan named Blackhole Rat, which the company first discovered Feb. 25.

A variant of the Remote Access Trojan darkComet, which targets Windows systems, Sophos Labs said that Blackhole Remote Access Trojan attacks the OS X operating system in a variety of ways. Via remote access, the Trojan allows attackers to remotely shut down systems, run commands, and send client computers to specified web addresses.

Sophos noted that the Blackhole Rat, which they referred to as MusMinim, was very basic and largely unfinished. More significant, however, was its presence on OS X, which suggests that the operating system may be presenting a more enticing target for malware developers.

Estimates of OS X's market share hover at around 7 percent, which security experts say explains the relatively small number of malware programs targeting the system. That number is set to rise, however, as Apple's share of the operating system market increases.

Likely in an effort to counter this, Apple released its developer preview for Mac OS X Lion to a number of security experts -- a first for the company.

Below is a video of the trojan running.

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