Like XP, and NT and 2K before them, They've been in battle for over a decade, being attacked, patched, attacked, Service Packed. Not invulnerable because nothing is, but 2K3 is better than it was, that being said, having a Windows box exposed to the internet with no protection is flat out silly. Right tool, right job. Using a windows 2003 server to serve webpages on the internet is like using a 6 yr old to direct traffic. All the requisite parts are there, but the execution isn't the best.