Hi Damdjo,
The Cisco botnet defense stuff is good at locating botnet activity within your network. However, Cisco doesn't at this time have a specific transparent spam filtering solution -- to my knowledge. You'll need to find a partner.
Fortunately, such a partner exists. MailChannels Transparent Antispam is designed to filter outbound spam, transparently, and to monitor the behavior of end-users. It connects with RADIUS so that users can be tracked based on their long term behavior -- rather than just the behavior of their IP address.
