A hacker group calling itself "DERP" has targeted a number of online gaming servers "for the lulz," or so they claim. DERP successfully took over servers like sony.com, EA.com, Battle.net and League of Legends, this achieved trough DDoSing. Denial-of-service attacks, something that hacktivist group Anonymous uses, lead to servers being overloaded by tons of activity and therefore lots of downtime.
While PlayStationNetwork.net was believed to be down due to a huge amount of new PS4 users, it transpired that DERP had managed to infiltrate it too. The servers are mostly back up, although they are still suffering some problematic periods.