Ryan Cleary, 19, and Jake Davis, 18, admitted being part of Lulzsec, an offshoot of the Anonymous collective. They and two others - Ryan Ackroyd, 25, and a 17-year-old boy - deny other similar hacking charges.
Lulzsec claimed responsibility for attacking the UK's Serious Organised Crime Agency (Soca) website. Mr Cleary, from Essex; Mr Davis, from the Shetland Isles; Mr Ackroyd from South Yorkshire and the unnamed 17-year-old will all face trial in April 2013.
Mr Cleary also faces charges in the US, where he stands accused of breaking into a number of websites, including that of the US X Factor, in order to deface them and steal personal details.
Lulzsec emerged as a splinter group of the Anonymous hacking collective in May 2011. Their name stood for Lulz Security - where "Lulz" is a play on words of the popular internet phrase "lol", meaning "laugh out loud". They employed techniques to flood websites with high traffic - known as a DDoS attack - in order to render them unusable.
Source: BBC News
