Bittrex just recently improved security by default for it's users. As all exchange users should be warned, even with 2FA your exchange accounts are extremely vulnerable with phishing. Bittrex does have additional options to whitelist your static IP(which is extremely advised) but now as default, you will be alerted when attempting access from a new IP.
This now requires confirmation of the new IP via email. Unless you've been severely compromised this is a very good additional safety measure. Whitelisting your static IP is still advised for even greater security.
Bittrex should certainly be given praise for enabling this as a default check. Perhaps this was in response to growing phishing attacks. I personally believe all exchanges need this as default measure. Good job Bittrex!