Twitter was taken offline for two hours due to a cascading bug in one of their infrastructure components that prevented users from logging in. Twitter officials dismissed any rumor that it was due to hacker attacks and said repairs would restore normal activity shortly. Twitter used to be notorious for its fail whale, but this is the first incident in six months that crippled the micro blogging platform. Rolling back the system kicks the platform back into shape but doesn’t reveal the nature of the bug.”]
Source: https://www.bitdefender.com/blog/hotforsecurity/twitter-silenced-by-cascading-bug/