Sony said the hackers appeared to have provided valid account IDs and passwords. The company said it would send email notifications and password reset procedures to the affected account holders.
Sony said less than 0.1 per cent of consumers of PSN, Sony Entertainment Network and Sony Online Entertainment Services might have been affected.
Credit card numbers related to the compromised accounts were not at risk, the company said.
Sony said the company had "taken steps to mitigate the activity" and was "continuing to investigate the extent of unauthorized activity on any of these accounts."
The unauthorized attempts took place between October 7 and 10.//DPA