For many budding computer hackers, the compulsion is like seeing a locked door and deciding to open it. It doesn't necessarily matter whose door it is or why it's locked in the first place. Sometimes the challenge is its own reward.

Commentators have speculated for years about the motivations that compel computer hackers - from glory among their peers, to the challenge factor, or the problem solving, or the laughs, or even out of malice - but the biggest factor behind successful hacking attempts is this: hackers attack complex network systems because they can.

But hackers themselves make fine and important distinctions between real hackers (themselves) and what they call the teenage cracker patrol: the latter are in the main the adolescent males who break into phone systems and public services to create chaos just for the hell of it. Crackers don't get much respect from more experienced hackers.

Consider the profiles that are emerging of the two young Irish men named by the FBI in the latest international hacking arrests this week; they share certain characteristics - quiet, shy, highly intelligent loners. They are crackers from central casting.

One of them, Darren Martyn, who is 19, now faces up to 20 years in prison for his efforts. On his Facebook page, his list of interest includes 'hacking computers,' 'ethical hacking' and 'lock picking.' Reports this week have revealed, ironically enough, that he runs a non-profit organization in Galway dedicated to making websites more secure. The full extent of his handiwork has yet to merge but it already sounds like it may have been conducted for kicks.

And we help to make it easy for them, albeit unwittingly. For most people adding a new friend to Google Circles is a complicated enough procedure - never mind locating the button to turn their new desktop on. Hackers thrive in a world this technophobic. While you're busy being intimidated by the latest tech innovations rolling out of Microsoft and Apple, they're busy unraveling the security that was supposed to protect you from their growing threat.

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If you think about it - and I get why people don't want to - the internet is a bit like leaving all the windows and doors in your house unlocked and walking away. There are so many holes in the security, so many potential exploits, that the implications of all that open access can be dizzying.

It's a mistake to trust the internet. It's not just the massive faceless organizations like the CIA or the FBI that are targeted by hackers and crackers, it's ordinary people too. Hackers (or more precisely, crackers) are not always principled or nice, as it happens. Sometimes they're just bored teenagers out for kicks.

When the cracker group LulzSec (which the two Irish crackers have been linked to this week) leaked the usernames and passwords of 62,000 random people off the internet earlier this month, their legions of fans on Twitter wrecked havoc on Amazon and Facebook with the stolen information culled from the attacks.

LulzSec said it did it for the hell of it, because it thrives on anarchy and because it could, and it felt no concern about what their young fans did to the public once the private passwords were released. That's nice isn't it? You're kidding yourself if you don't think it could happen to you. Hackers built the internet and they know how to destroy it too. You'd do well to remember that every time you hear your start-up chime.

But when reading the reports about the latest hacking arrests, try to remember that there are white hats and black hats on the internet too. Hackers build things like open source software and good computer code but crackers just take things apart and go to prison for it.

The tragedy for Darren Martyn and his Irish cohort Donncha O Cearbhaill is that they aligned themselves with a freewheeling destructive force on the internet. Ireland will face repercussion from crackers for permitting their arrests. The rest of us should wake up to the extent of the threat.