Two experts in the field of cyber forensics and psychology have some answers to that question. One is Marc Rogers, a behavioral sciences researcher at the University of Manitoba in Winnipeg, Canada, and a former cyber detective. The other is Jerrold M. Post, a psychiatrist at George Washington University in Washington, D.C.

Rogers and Post have identified some basic behavioral trends for hackers who commit crimes. Rogers says one characteristic is that they tend to minimize or misconstrue the consequences of their activities, rationalizing that their behavior is really performing a service to society. (Some researchers call this the Robin Hood Syndrome). They may also tend to dehumanize and blame the victim sites they attack. Post says the same hackers share a sense of "ethical flexibility," which means that since human contact is minimized over the computer, hacking becomes like a game where the serious consequences can be easily ignored.

But Rogers is careful to point out that not all hackers are criminals. He's identified four categories as follows:

1. Old School Hackers: These are your 1960s style computer programmers from Stanford or MIT for whom the term hacking is a badge of honor. They're interested in lines of code and analyzing systems, but what they do is not related to criminal activity. They don't have a malicious intent, though they may have a lack of concern for privacy and proprietary information because they believe the Internet was designed to be an open system.

2. Script Kiddies, or Cyber-Punks: Most commonly what the media calls "hackers." These are the kids, like Mafia Boy, who most frequently get caught by authorities because they brag online about their exploits. As an age group, they can be between 12 and 30 years old, they're predominantly white and male, and on average have a grade 12 education. Bored in school, very adept with computers and technology, they download scripts or hack into systems with the intent to vandalize or disrupt systems.

3. Professional Criminals, or Crackers: These guys make a living breaking into systems and selling the information. They might get hired for corporate or government espionage. They may also have ties to organized criminal groups.

4. Coders and Virus Writers: Not a lot of research has been done on these guys. They like to see themselves as an elite. They have a lot of programming background and write code but won't use it themselves. They have their own networks to experiment with, which they call "Zoos." They leave it to others to introduce their codes into "The Wild," or the Internet.

Underlying the psyche of the criminal hacker may be a deep sense of inferiority. Consequently, the mastery of computer technology, or the shut down of a major site, might give them a sense of power. "It's a population that takes refuge in computers because of their problems sustaining real world relationships," says Post. "Causing millions of dollars of damage is a real power trip."