Yahoo said it believes that at least 500 million user account credentials were stolen, which would make it the biggest breach of all time — bigger than the Myspace breach of 360 million user accounts and 427 million passwords. The breach has turned out to be larger than the 200 million accounts previously expected.
http://www.businessinsider.com/yahoo-hack-by-state-sponsored-actor-biggest-of-all-time-2016-9