One of the most interesting sessions I have seen on security was presented at Tech ED by Marcus Murray back in 2006.  From his blog it looks like he is still impressing people by doing his presentations.  He focuses not only on traditional network attacks but also physical security of his network.  One of the interesting stories he talks about is dropping flash drives in the parking lot of a company.  Inevitable one of the company employees will take a flash drive and plug it into their computer.  The flash drive then installs software that reports back to him.  He then has control of the users machine.  It is a pretty scary demonstration that shows just how vulnerable a company is.  I would strongly encourage you to watch the below presentation.  It will give you a new outlook on how you view network security at your current job.

Recorded Presentation
http://www.microsoft.com/emea/spotlight/sessionh.aspx?videoid=351

Marcus Murray’s Blog
http://truesecurity.se/blogs/murray/default.aspx