Been a while since I have done an update but i came across something pretty cool i wanted to share: ASA Botnet filter.
This feature (available on all ASA's version 8.2 and above) basically does what it says on the label: Tracks and reports back on any suspicious activity leaving your network that looks like one of your boxes may be infected. It of course is constantly updated with new botnet-like patterns so it should be able to detect all the latest bot's as they come out.
It is a licensed feature but a 30 day trial is available, check out:
for more details