This is a cut and paste, but since many people here use Bittrex, I thought it was important to spread the word.
October 30th, 2016Due to the large number of leaked username and password databases, we are making changes to withdrawals to limit the damage of unauthorized access to your account. This is not a substitute to having strong and unique passwords, protecting your email account, and having 2 factor authentication on your Bittrex account. Bittrex strongly encourages you to have 2 factor authentication. (See the link below for full story)
https://bittrex.zendesk.com/hc/en-us/articles/231701788