The original network intruders were often misfit geeks operating from boredom or a need for thrills. As businesses went online, a new kind of intruder arose  a thief, poking around for credit card numbers or a chance to add another spam slave to the botnet.

This new breed of intruder brings a sophistication that takes the threat to the level of cyber attack. Well-funded and highly skilled criminal organizations can stake out a network for months  sometimes years, keeping constant watch and trying every trick they know until they find a way to slip past security. Many of these organizations aren't just looking for a single hit  they want to stay on the network for the long term and generate revenue by stealing financial data, medical data, and trade secrets.