In the spotlight are "crackers" - computer hackers with an axe to grind.

Contrary to popular belief, most hackers are not malicious. They see themselves as cyber-altruists; builders, whose goal is not to damage or destroy networks but to improve them by exposing programming flaws.

Penetrating a system is known as an "exploit". Once completed, a hacker will report the problem to the makers letting them know the system is open to attack.

It is not necessarily legal, but hackers enjoy the challenge and if they remain circumspect the victim may even appreciate the "service".

Some hackers even turn legitimate and are paid by companies to find weaknesses in their systems.

Crackers, however, have no time for this type of softly-softly approach. They are seen as "cyber-terrorists" - headline-grabbers intent on generating as much fuss as possible, which usually means employing destructive tactics.

The term "cracker" was coined by hackers in the mid 1980s in an effort to distance themselves from the ruinous work of irresponsible teenages. Its definition has widened and there are now several interpretations.

Crackers have often hit the front pages. Often those responsible have a "political" or ideological reason for picking who to target.

Earlier this month, a group of crackers calling itself the United Loan Gunmen broke into the Website of ABC television and replaced the home page with a screed of anti-corporate statements.

In broken English, the crackers left a message urging individuals to seize control of the media.

New York Times on the web - also a target

"Television and other forms of elderly media is slowly being drown out as more an more people are looking to there computers for there information and entertainment," the message read.

Last year, crackers calling themselves Hacking for Girlies broke into the New York Times Website and plastered the front page with pornographic images.

This time the target was thought to have been Times journalist John Markoff, co-author of a book about super-cracker, Kevin Mitnick.

Mitnick, currently serving a 46-month prison term, is known as the king of computer crackers.

Kevin Mitnick - the king of computer crackers

He pleaded guilty to charges of computer and wire fraud having been accused of attacking systems belonging to, among others, Motorola, Nokia, Fujitsu, Novell, NEC, and Sun Microsystems.

Indeed, Microsoft, which owns the Hotmail service which was hacked by group calling itself Hackers Unite, is no stranger to attacks from hardcore computing devotees.

Crackers have even developed software, such as Back Orifice - a play on the company's Back Office program - which is designed to wreak havoc on any system using a version of Windows.

The programmers who broke open Hotmail say they did so to expose poor security. But their dramatic tactics have gained them the biggest headlines yet.