Here's Art Gorski's take on the issue. "Regarding the PMUG news item, [in the earlier posting on this site] this is basically a spam email. There is currently no need for antivirus software for the Mac. The 'botnet' quoted does exist, although it is tiny, and those Macs got infected by downloading illegal software, so they got what they deserved. :-)"
Allen Laudenslager adds, "This is not a huge attack on Macs. So far it is only attacking Macs that use a pirated version of iWork. One more reason to buy from Apple." See this article,
http://www.cnn.com/2009/TECH/04/22/first.mac.botnet/index.html