In a blog post Sony said that no personal information had been accessed.
On Sunday an American Airlines flight carrying a senior Sony executive was also diverted following a bomb scare.
The group claiming responsibility for closing down the network also tweeted suggesting there was a security threat to the flight.'Fixing the issue'
In a blog Sony said that "the PlayStation Network and Sony Entertainment Network have been impacted by an attempt to overwhelm our network with artificially high traffic".
"We will continue to work towards fixing this issue and hope to have our services up and running as soon as possible," the blog said.
Sony has said the FBI is investigating the security scare over the flight carrying Sony Online Entertainment President John Smedley, which should have landed in San Diego but was diverted to Phoenix, Arizona.
Mr Smedley tweeted, "Yes. My plane was diverted. Not going to discuss more than that. Justice will find these guys."
Sony's 52 million strong PlayStation network has been hit by hacking attacks before, including a security breach in 2011.
Sony had already scheduled routine maintenance work to be done on its PlayStation network on Monday.
After 1740 BST some services including PlayStation Store, PSN account management and registration, entertainment services and online gameplay will be unavailable.