Little is known about the LulSec group, although they have claimed responsibility for recent attacks on several websites in the USA - Fox, PBS and XFactor.
It is understood to be a separate organisation from Anonymous, the "hacker collective" which has been linked to a number of high profile web attacks including several on Sony sites.
The latest attack has, once again, raised questions about the strength of security employed by Sony and other companies holding sensitive user data.

Much of the information taken in the Sony hacks was unencrypted and easily readable.
Mike Smart from cryptography specialists Safenet said that many companies were only applying their highest security protocols to data such as credit card numbers.
He explained that other "social" information was often given minimal protection.
"People can get through the front door. Now we have got to the stage that we need to lock the inside doors and put our documents in a safe.