How to Manually Detect If You're Infected With the OS X Flashback Trojan
f-secure.com
f-secure.com
tl;dr version:
In terminal run these:
defaults read /Applications/Safari.app/Contents/Info LSEnvironment
defaults read ~/.MacOSX/environment DYLD_INSERT_LIBRARIES
if both are not found you are clear. If found, read the f-secure article.