We blocked tftp and MSRPC at our perimeter and that worked for a good while; however, should have paid more attention to our backdoors (dialup/vpn). That opened the door before we could close it again...of course now we are and have blocked/monitored there as well and aside from the occasionaly schmuck bringing in infected laptops things have been pretty quiet...

Guess the point is, even with a good hard perimeter...a soft gooy center still leaves you open to other threats, it is just a matter of time (be it a backdoor, people plugging up other equipment, etc). Best thing you can do is make sure you are not vulnerable by using a scanner (Retina has one that is free for this vulnerability and I think the SANS folks released one too) and to patch up any vulnerable machines.

/nebulus