Wired points to a couple of recent stories by ZDNet writer Ed Bott marking the first wide-spread trojan infections in the Mac community.

The trojan horse is called Mac Defender. It’s a web pop-up containing a spoof message that tells customers their machines are infected by a virus and they must install anti-virus software. If customers agree to install the software, the program sporadically loads porn websites on their computer.

ZDNet writer Ed Bott was first to spot a long thread of complaints in Apple’s support forums related to Mac Defender, with at least 200 posts of customers reporting they’ve been infected by the malware.

“I’ve done similar searches in the past … [and] I have never found more than one or two in-the-wild reports,” Bott wrote. “This time, the volume is truly exceptional.”

This seems likely to be the first of many instances. As Apple continues to increase market share, malware writers are increasingly likely to focus their efforts on the growing Mac market.