We're locked down pretty good here,but there always seems to be some things that get through, it's the nature of the beast.   Windows Vista fixed a lot of that problem (XP let a LOT of things through), but even there we get some stray programs installed.

Things like Google Desktop, Windows Desktop search may not be blocked via your policies, and will bring computers to a slow motion state, which can affect authentication.   IE plug-ins are also notorious for being installed on a locked-down computer and interfering with web browser authentication.

The program that is giving me the biggest fits lately has been iTunes, although if you have a tightly locked-down system it probably won't be there.  They insist they need it here "for educational purposes", so it gets installed.   That program loves to install it's own peer-to-peer network, and even puts in it's own DNS responder!  We had to invest many thousands of dollars into additional networking equipment since the latest versions of that program came out just to segregate our network into smaller segments to keep iTunes from knocking it down. *sigh*

It's done in DNN 5. There wasn't a field for it in DNN 4 that I know of.