Allegedly, Cleary and other LulzSec members would exploit security vulnerabilities in the sites of major companies to gain unauthorized access to administrative panels. Many of the sites were defaced while others were completely taken down.
Cleary was arrested last year in the UK over allegations he hacked various British music sites and law enforcement agencies.
In the PBS hack, Cleary and LulzSec posted a fake story claiming deceased rapper Tupac Shakur was actually living in New Zealand. The hits on Sony and Fox were to steal personal info.
The young adult faces up to 25 years in prison.