The suspected leader of the hacking group Lulzsec has pleaded guilty to carrying out high profile attacks on several companies.
Hector Xavier Monsegur had been charged with conspiracy to engage in computer hacking according to unsealed court papers filed in Manhattan.
Reuters reports that the charges were filed via "a criminal information".
The news agency says that suggests that the suspect - nicknamed Sabu - had co-operated with the government.
US law enforcement officers have said at least three members of the hacking group had been arrested.
Irish police added that they have arrested one of five men being sought in connection with the group and are holding him at a south Dublin police station.
Charges against other suspects are expected to be made public later.
The collective, which is linked to the online activist group Anonymous, had claimed responsibility for attacks against eBay and Sony Pictures among others.
'For the Lulz'
Lulzsec claimed responsibility for exposing security flaws in some of the world's most high-profile systems:
Last month Anonymous published a recording of a private telephone conversation between FBI agents and London detectives talking Lulzsec suspects.
- 30 May 2011 - Lulzsec members hack into the website of US broadcaster PBS, posting a fake story suggesting deceased rapper Tupac Shakur was still alive and living in New Zealand.
- 2 June - The group attacks Sony Pictures Entertainment, releasing usernames, email addresses and phone numbers of competition entrants.
- 16 June - Lulzsec claims to have caused technical disruption to the website of the CIA.
- 20 June - The website of the UK's Serious Organised Crime Agency (Soca) is taken offline in an apparent "denial of service" attack.
Fox News reported that one of Lulzsec's leading members had helped the bureau gather evidence against his associates.
The news organisation quoted one FBI official as saying: "This is devastating to the organisation... we're chopping off the head of Lulzsec."
Prof Alan Woodward, from the University of Surrey's department of computing noted that Lulzsec had been quiet since the middle of 2011 following an attack on Paypal.
"Judging by the level of activity this morning, where hackers have been pasting personal information about the person reported as having turned witness to implicate other hackers, it would appear that there is a considerable rift inside these groups," he said.
"The hackers are certainly acting as if they feel they have been betrayed by one of their own."