In a letter from Kazuo Hirai, Chairman of the Board of Directors of SCEA, to the U.S. House of Representatives the company has claimed that the intruders who hacked into the SOE servers planted a file on them that points to the hacker group Anonymous.
Hirai did not state in the letter what the purpose of the file was, but said that it was named “Anonymous” and contained the group’s tag line “We are Legion”.
In a separate statement to Joystiq a SOE rep stated that both the PSN and SOE systems are “operated separately” but there is “some degree of architecture that overlaps” between them. Because of similarities between both intrusions SOE stated that they do NOT consider the SOE hack as a “second attack” but believe both hacks were made from the same party.
Anonymous has stated that they are not responsible for the attack.
Source: PlayStation Blog