There are 1.9 billion stolen passwords and usernames available on the black market, and up to 25% of them will still work on a Google account (GOOG, GOOGL)
Billions of stolen user names and passwords are available on black market forums.Using internal Google data, researchers found between 7% and 25% of these stolen passwords would work on a Google search or Gmail account. Gmail, Yahoo, and Hotmail users make up 50% of the victims of stolen passwords in the study — even though the passwords were stolen from different services such as MySpace or LinkedIn.
Source:: https://finance.yahoo.com/news/1-9-billion-stolen-passwords-173207888.html