The FBI is facing questions over its role in a 2011 hacking attack on Rupert Murdoch's Sun newspaper in the UK after the publication of chat logs showed that a man acting as an agency informant played a substantial role in the operation. The attack was so successful that the publisher took down the websites of the Sun and the Times while technicians worked out the scale of the hack. Unsealed documents ... seen by the Guardian, show Hector Xavier Monsegur - known widely online as Sabu" and frequently referred to as the leader of Lulzsec - played an active role in the operation. The chat records show Monsegur encouraging others to break further into News International systems, claiming to have sources at the Sun, and even apparently helping to break staff's passwords and to source files for stealing. Monsegur was, however, at that time operating under the direction of the FBI. The close involvement of an FBI asset working under extraordinarily close supervision in a hacking attack on a media outlet ultimately owned by a US-listed company is set to raise further questions about the agency's approach to tackling online crime. The logs also show Sabu on multiple occasions offering detailed technical help to find additional records on different servers, breaking in to new servers, or obtaining more files - which could easily have included those belonging to journalists at either the Sun or Times. The Sun, which is challenging the UK government over police accessing the phone records of one of its reporters, declined to comment on the apparent FBI involvement in attacks on its servers.