Flashback is the latest attempt to infiltrate Macs as of April 7, 2012.
It is described here http://www.f-secure.com/v-descs/trojan-downloader_osx_flashback_i.shtml
And further reference is on http://www.f-secure.com/v-descs/trojan-downloader_osx_flashback_k.shtml
Now a more thorough test of whether or not you have is available with a simple script from one of the other volunteers of
the forum, etresoft: