I wanted to add a bit more context/info/explanation on Purple Teaming after publishing the Ruxcon slides as well as Facebook and Twitter interactions on that topic.
What is Purple Teaming?
Currently, there are as many definitions for Purple Teaming as there are talks and blog posts on the subject but I'm going to throw mine in as well.
Purple Teaming is "conducting focused pentesting (up to Red Teaming) with clear training objectives for the Blue Team."
The clear training objectives (aka a plan to eventually get caught) for the Blue Team is what differentiates Purple Teaming from typical Red Teaming. By its very nature, Red Teaming is making a HUGE attempt not to get caught. You are pulling out all the tips & tricks and big boy tools NOT to get caught. With Purple Teaming, you have a plan to create an alert or event in the event the Red Team is not detected by the Blue Team during the Red Team process so the Blue Team can test their signatures and alerting and execute their incident response policies and procedures.
It isn't a "can you get access to X" exercise it is a "train the Blue Team on X" exercise. The pentesting activities are a means to conduct realistic training.
A couple practical examples:
The Blue Team has created alerts to identify Sysinternals PsExec usage in the enterprise. The Red Team would at some point use PsExec to see if alerts fire off and the Blue Team can determine which hosts were accessed or pivoted from using PsExec. The Red Team could also make use of all the PsExec alternatives (winexe, msf psexec, impacket, etc) so the Blue Team could continue to refine and improve their monitoring and alerting.
Another scenario would be where the Blue Team manager feels like the team has a good handle on the Windows side of things but less so on the OSX/Linux side of the house. The manager could dictate to the Red Team that they should stay off Windows Infrastructure to identify gaps in host instrumentation and network coverage for *nix types hosts and also to force incident response on OSX or Linux hosts.
Another example could be to require the Red Team not to utilize freely available Remote Access Trojans such as Metasploit or powershell Empire. Instead they could ask that the Red Team purchase (or identify a consultancy that already uses) something like Core Impact or Immunity's Innuendo or find a consultancy that has their own custom backdoor to spice things up.
Other Purple Teaming resources (in no particular order):