Dropbox added support for USB key authentication. The new feature can be utilized as part of a two-step verification - user will insert the USB key after typing their password instead of entering digits.
The feature requires a FIDO Universal 2nd Factor-compatible USB key, which can also work with other U2F authentication accounts, including from Google. Currently, the new login security feature is only available through a Chrome web browser.
USB key login will surely appeal to those who are worried about using their account credentials in a phishing attack. Users who lose their U2F key will still be able to access their account via an authenticator app or a text message.