A Scots teenager had admitted hacking into the website of the Serious Organised Crime Agency and other prominent organisations.
Jake Davis, 19, admitted conspiring to carry out a "denial of service" attack on the crime agency.
He also admitted hacking the NHS website at Southwark Crown Court on Monday.
Davis, 19, and Ryan Cleary, 20, denied other charges in relation to obtaining confidential data and posting on other sites like Lulzsec.
Davis, from the island of Yell, faced five charges following a Met Police investigation into the hacking groups LulzSec and Anonymous.
They have been linked to a number of so called cyber-attacks on government agencies and multi-national companies.
He was said to have used the online nickname "Topiary" and presented himself as a spokesman for the two groups.
LulzSec has also been linked to hacking attempts on the NHS, Sony, and The Sun newspaper.
The teenager faced five charges, including conspiring to carry out a distributed denial of service attack on the police agency. Such attacks see websites flooded with traffic, which makes them crash.
Davis was also charged with gaining unauthorised access to a computer system, encouraging or assisting offences and with two counts of conspiracy to commit offences.
At a hearing in August 2011, the teenager was bailed to an address in Spalding, Lincolnshire, where his mother lives. The judge imposed a curfew from 10pm to 7am, ordering Davis to wear an electronic tag.
He was also told he was not allowed to access the internet through a computer or mobile phone, either himself or by asking someone to do it for him.
The Director of Public Prosecutions is to decide whether Davis and Cleary should face trial. The case has been adjourned until July 12.