GFI Languard NSS...

"GFI LANguard Network Security Scanner (N.S.S.) checks your network for all potential methods that a hacker might use to attack your network. By analyzing the operating system and the applications running on your network, GFI LANguard N.S.S. identifies possible security holes. In other words, it plays the devil's advocate and alerts you to weaknesses before a hacker can find them, enabling you to deal with these issues before a hacker can exploit them."

It does much more and is free for non commercial users...