also - "unauthorized" is actually "unauthorised" but spell check wouldn't pick that up, because it's the american spelling

---------- Post added at 12:01 ---------- Previous post was at 11:57 ----------
Also - on a bit of an addition, he hasn't mentioned NAT (Network Address Translation) in the bit about unauthorised network access part... NAT is important as it separates external IP's from Internal IPs and is a security feature also.
A company that doesn't use NAT, may give each PC an externally accessible IP address, whereas with NAT, you only need one (or a few) external IP addresses, and so all company computers aren't as easily hacked into.