Julian Assange helped research a great book called "Underground: Tales of Hacking, Madness and Obsession on the Electronic Frontier"
Documents the antics (and downfalls) of various hackers from the late 80s and early 90s, most of them Australian. Assange (aka Mendax) is one of the hackers the book follows.
It's out of print these days, but the author, Suelette Dreyfus made the book available online back in 2001 - http://underground-book.net/
I guess Nortel didn't learn from that lesson and secure their network.