Blizzard through Battle.net is experiencing server issues and queues from a DDoS attack
The attacks are ongoing with little details about how long they could last.

Image via Infinity ward
Tonight Blizzard and Battle.net are experiencing server issues and extensively long queues affecting a variety of games, such as Call of Duty: Modern Warfare and Overwatch. It appears the Blizzard servers were handling a heavy DDoS attack and were having trouble connecting players to their games.
Blizzard’s Twitter accounts have referenced the attacks, but the company said it doesn’t know how long they could last. Because these attacks are recent and still ongoing, we’ll have to wait to hear more details. Hopefully, due to social distancing and self-quarantining recommendations to help manage the coronavirus, these attacks do not continue for much longer. Xbox Live was already gone for a good chunk of the afternoon on March 15.