Nothing here is new, but a generaly good read.

Exerpt

{The ARPA Computer Network is susceptible to security violations for at least the three following reasons:

(1) Individual sites, used to physical limitations on machine access, have not yet taken sufficient precautions toward securing their systems against unauthorized remote use. For example, many people still use passwords which are easy to guess: their fist names, their initials, their host name spelled backwards, a string of characters which are easy to type in sequence (e.g. ZXCVBNM).

(2) The TIP allows access to the ARPANET to a much wider audience than is thought or intended. TIP phone numbers are posted, like those scribbled hastily on the walls of phone booths and men's rooms. The TIP required no user identification before giving service. Thus, many people, including those who used to spend their time ripping off Ma Bell, get access to our stockings in a most anonymous way.

(3) There is lingering affection for the challenge of breaking someone's system. This affection lingers despite the fact that everyone knows that it's easy to break systems, even easier to crash them.

All of this would be quite humorous and cause for raucous eye winking and elbow nudging, if it weren't for the fact that in recent weeks at least two major serving hosts were crashed under suspicious circumstances by people who knew what they were risking; on yet a third system, the system wheel password was compromised -- by two high school students in Los Angeles no less.

We suspect that the number of dangerous security violations is larger than any of us know is growing. You are advised not to sit "in hope that Saint Nicholas would soon be there".}

Basics of Spoofing, a good read for those interested in networking.