As you might remember, on Match 16th Microsoft together with other industry players was successfully able to take down the Rustock botnet and thus significantly reducing the spam level.
We now just published a special Intelligence Report on this botnet:
Read an overview of the Win32/Rustock family of rootkit-enabled backdoor Trojans background, functionality, how it works, and threat telemetry data with analysis for 2010 to May 2011. This document provides legal and technical action used to takedown the Rustock botnet and how to detect and remove the threat using Microsoft antimalware products.
You will find it here.