Sony Online Entertainment president John Smedley said the low hacking success rate made it unlikely that account information was taken from their databases.
"It's just simple math. There was such a small percentage of successes. They were attacking with a large number," he told GameSpot.
"Because of that, the math tells us it wasn't [Sony's information]. We've said publicly when we were compromised before that the information is out there and could have been used. That was obviously the first thing we looked at.
"Then we did the mathematical analysis and said, 'Obviously that's not what happened'. I'm not going to say it's impossible [the info came from Sony]. We just think that's not the most likely case."
Smedley added that the latest hacking targeted "dormant accounts" but still urged users to change their passwords as a precaution.
Yesterday, 93,000 PSN and SOE accounts were suspended following "a large amount of authorised sign-in attempts".
The PlayStation Network was taken down in April following hacker activity. Sony executive Tim Schaaff recently described the hacking as "a great learning experience", but added: "I would not like to do it again."