Welcome to our world.:(
For years, Mac users have long been rightfully smug about their platform's relative immunity to virus and malware attacks, but it's inevitable that those days will eventually come to an end. (As the Mac gains in popularity, it also earns more attention from malware developers, and it's this lack of malware being actively developed, not some special, inherent security, that have really kept the Mac a "safe" platform for the time being.)
Now we're seeing one of the first moderately-sized exploits to take advantage of Mac users. The iServices.A Trojan horse is an attack being distributed via BitTorrent, where it's disguised as a bootleg copy of the new iWork 09. Once installed, the malware takes administrator access and connects to remote servers over the Internet, where it can be given additional instructions as the author commands, from installing additional malware to stealing information off the Mac in question. The malware creator can also take complete remote control of any compromised machine.
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http://tech.yahoo.com/blogs/null/117188