The design of a Corporate gateway to the Internet must deal with the classical tradeoff between security and convenience. Most institutions opt for convenience and use a simple router between their internal internets and the rest of the world. This is dangerous. Strangers on the Internet can reach and test every internal machine. With workstations sitting on many desks, system administration is often decentralized and neglected.
Passwords are weak or missing.
A professor or researcher often may install the operating system and forget it, leaving well-known security holes uncorrected. For example, a sweep of 1,300 machines inside Bell Labs around the time of the Internet Worm found over 300 that had at least one of several known security holes. Until its disconnection a little while ago, this VAX 750 handled all the Internet mail traffic and other services for the company. ARPA had Ethernet connections to both the inside and outside Internets, just like a router. It could also make and accept calls on our corporate Datakit network.