SATAN (Security Administrator Tool for Analyzing Networks) was written by myself and my erstwhile collegue, Wietse Venema, and was originally released on April 5th, 1995.

Just putting it here for its final resting home. There's a type of web demo we'd put together that may (at least currently) be viewed on my website:

http://fish2.com/satan/

(The original fish.com was sold off for pieces o' eight.)

It may have been the first web program, with a real web GUI, backend DB, etc. But then again, it may not have been, who really knows?

Best of luck to all in the new millennium.