Sony is investigating the possibility of "targeted behaviour by an outside party" as the PlayStation Network continues to remain offline across the US and Europe.
It has been impossible to sign in to the PlayStation Network throughout today.
This morning Sony described the problem as an "outage", but in a new message posted on the EU PlayStation Blog, manager James Gallagher suggested hackers may be responsible.
"As you are no doubt aware, the current emergency outage is continuing this afternoon and all Sony Online Network services remain unavailable," he said.
"Our support teams are investigating the cause of the problem, including the possibility of targeted behaviour by an outside party. If the reported Network problems are indeed caused by such acts, we would like to once again thank our customers who have borne the brunt of the attack through interrupted service.
"Our engineers are continuing to work to restore and maintain the services, and we appreciate our customers' continued support."
The Anonymous group, upset at Sony and George "Geohot" Hotz' out of court settlement over the PlayStation 3 jailbreak lawsuit, declared war on Sony earlier this month.
In a video posted to YouTube last week, Anonymous promised to deliver "the biggest attack you have ever witnessed".
However, earlier this month Anonymous "temporarily suspended" its war on the PlayStation Network – saying its beef was with Sony, not Sony's customers.
"Anonymous is not attacking the PSN at this time," Anonymous said. "We realise that targeting the PSN is not a good idea. We have therefore temporarily suspended our action, until a method is found that will not severely impact Sony customers.
"Anonymous is on your side, standing up for your rights. We are not aiming to attack customers of Sony. This attack is aimed solely at Sony, and we will try our best to not affect the gamers, as this would defeat the purpose of our actions. If we did inconvenience users, please know that this was not our goal.
"This operation is a response to Sony's attempt to deprive their customers of products they bought and therefore own, wholly and completely. Anonymous will not attempt to fight this by following the exact same course of action.
"We have plenty of tricks up our sleeves."