Sony has confirmed that a hacking attack was to blame for its PlayStation Network being taken offline.
The company said that it had taken the PSN down voluntarily while it investigated an "external intrusion".
The system is still unavailable five days after the hack was discovered.
Users trying to connect have been met with error messages stating that the network is "undergoing maintenance" or is "suspended".
The PlayStation Network is used by owners of PS3 and PlayStation Portable machines to download games, films and music, as well as to play online with friends.
According to Sony, it has more than 70m accounts registered worldwide.
In a blog post, the company thanked users for their patience and assured them that it was working "around the clock" to strengthen the network infrastructure.
"Though this task is time-consuming, we decided it was worth the time necessary to provide the system with additional security," wrote Patrick Seybold, the company's senior director of corporate communications and social media.
The statement did not address the issue of personal information, including credit card details, stored by PSN.