Ryan Ackroyd, Jake Davis and Mustafa Al-Bassam pleaded guilty to one charge of carrying out an unauthorized act to impair the operation of a computer. The men are said to have carried out distributed denial of service (DDoS) attacks on the institutions with other unidentified hackers belonging to online groups such as LulzSec, Anonymous and Internet Feds. The group, an offshoot of the Anonymous hacktivists, wreaked havoc throughout 2011 and 2012, knocking thousands of websites offline and pilfering data.
Source: https://thehackernews.com/2013/04/three-lulzsec-hackers-pleads-guilty-to.html