The Playstation Network has been experiencing some outages the past 12 hours or so due to hacking attempts. Sony issued a statement via Twitter stating that they are aware of issues that some users are experiencing and were working to address them:
Microsoft have also been experiencing similar issues with network issues, hacking group 'Lizard Squad' have been claiming responsibility for those issues, and are now claiming to be behind the PSN problems too.
Sony have had issues with hackers for the past several weeks, however they seem to have the recent spate of attacks under control.
No doubt this is the start of a lengthy and tedious cat and mouse game between the Sony, Microsoft and the hacking group, so stay tuned for any further developments.