Sony has delayed the relaunch of its online PlayStation video game network.
It had previously said the network would resume normal operations by the weekend.
Sony recently suffered a huge security breach with the theft of personal data from 100m online accounts.
"We were unaware of the extent of the attack on Sony Online Entertainment servers, and we are taking this opportunity to conduct further testing," Sony said in a blog.
"We won't restore the services until we can test the system's strength in these respects."
The security breach was first discovered on 20 April.
Many users have been upset about the company taking two days after discovering the theft before contacting the police and almost a week to inform those people affected.
Also over the weekend, Sony admitted that it had found some 2,500 names and partial mailing addresses of customers posted by hackers on a website.
Sony said it immediately took down the site, and were removing any residual links to the list.
"The website was out-of-date and inactive when discovered as part of the continued attacks on Sony," it said in a statement.
The data belonged mostly to US customers who took part in a competition in 2001.
Last week, in a bid to reassure Sony's customers and regain their trust, Chief Executive Howard Stringer said that "to date, there is no confirmed evidence any credit card or personal information has been misused, and we continue to monitor the situation closely."
In a blog post on the PlayStation website, he wrote that the company was working on heightening security measures to "protect your information better than ever".
He also offered compensation to US PlayStation Network and Qriocity users in the form of a year-long free enrollment in an identity protection programme.
The programme includes a $1m (£608,000) identity theft insurance policy for each user, should they become victims of any future cyber-attacks.