After both Sony and Playstation websites went down for many users as a result of a possible DDOS attack, it looks like PSN is also affected as Sony’s confirmed that the service will be going sporadic maintanance throughout today and users might experience problems connecting to their accounts.
They informed this via a tweet:
PSN currently undergoing sporadic maintenance. Access to the PSN may be interrupted throughout the day. We apologize for any inconvenience.
You can read more about the DDOS attack over here