Overwatch servers down, Lizard Squad suspected

{Overwatch} servers are currently either down or login times are very slow. Blizzard announced this via Twitter by saying:

"We're currently investigating an issue affecting our authentication servers, which may result in failed or slow login attempts."

There's no mention here of an attack specifically, but a member of the hacker group Lizard Squad then wrote the following:

"Hai there @BlizzardCS
Don't mind me, just doing some preparations.
Take care of my packets, Thanks?"

Blizzard has yet to announce what has caused the server malfunction.