LONDON -- A British computer hacker affiliated with the group Lulz Security has pleaded guilty to cyberattacks on institutions including Sony, Britain's National Health Service and Rupert Murdoch's News International.

Ryan Ackroyd pleaded guilty Tuesday at London's Southwark Crown Court to carrying out an unauthorized act to impair the operation of a computer.

Prosecutors say the 26-year-old accessed websites for Sony, 20th Century Fox, the NHS, Nintendo, the Arizona State Police and News International between February and September 2011.

He will be sentenced May 14.

Three other hackers -- 18-year-old Mustafa Al-Bassam, 20-year-old Jake Davis and 21-year-old Ryan Cleary -- also have pleaded guilty to launching cyberattacks on organizations including the CIA and Britain's Serious Organized Crime Agency.