6 March 2012updated 26 Sep 2015 8:16pm

Leader of hacking group LulzSec was working with the FBI

International swoop sees 5 people arrested, as it is revealed that "Sabu" had turned informant.

The secretive community of internet hackers has been shaken today as the FBI has arrested or charged five members of the hacking group LulzSec. In a dramatic sequence of events, it was revealed that the head of the group, who used the name “Sabu”, has been working for the FBI since the middle of last year.

Sabu, whose real name is Hector Xavier Monsegur, is a 28 year old unemployed Puerto Rican living in New York. He has been charged with 12 criminal counts of conspiracy to engage in computer hacking and other crimes. He has pleaded guilty to carrying out online attacks against PayPal and Mastercard.

LulzSec, a group of up to 10 people, stormed the hacking scene last year, attacking high profile targets including Sony, the CIA, the US Senate, and the FBI. After this explosive start, it announced abruptly in June that it would leave the hacking world. It wasn’t quite the end though. The group continued to carry out some attacks against targets including Rupert Murdoch’s News Corporation.

Back in June, the Guardian published leaked chat logs which gave an insight into internal tensions in the organisation:

The group’s ambitions went too far for some of its members: when the group hit an FBI-affiliated site on 3 June, two lost their nerve and quit, fearing reprisals from the US government. After revealing that the two, “recursion” and “devrandom” have quit, saying they were “not up for the heat”, Sabu tells the remaining members: “You realise we smacked the FBI today. This means everyone in here must remain extremely secure.”

Fox News, which broke the story, quoted an unnamed FBI official:

This is devastating to the organization. We’re chopping off the head of LulzSec.

Both Fox News and the FBI have reason to be pleased about this, as they’ve both been targeted by LulzSec in the past.

The worry in the hacking community will be that these five arrests — two in the UK, two in Ireland, and one in Chicago — could be just the tip of the iceberg. The co-operation of Monsegur could mean arrests not only of other members of LulzSec but of others within the broader hacking collective, Anonymous, from which the smaller group sprung. It is necessarily a very paranoid world, and this development will do nothing to appease these fears about security.