The easiest way to set up an app is to fire up your authenticator app and use your phone’s camera to scan the two dimensional barcode that Dropbox provides. Click Enable Two-step Verification, and you’re all set. It’s best to write this down and stow it somewhere secure where you can get at it (and especially where it’s not stored in Dropbox itself). You’ll then be provided with a 16-character emergency backup code which can be used to disable two-step verification just in case you can’t access your phone for some reason. Once you’ve entered the phone number, you’ll receive a text message with a six-digit code, which you’ll use to verify that yes, that is the phone you meant to use. If you choose text message, you’ll be asked to provide a phone number to which codes will be sent whenever you sign in to the Dropbox website or link a new device to your account. However, smartphone users will likely be better served by a mobile app, since it can work even when your phone isn’t connected to the network. Each option has its own virtues: If you’re using a non-smartphone, you’ll probably want to opt for standard text messages. After that, you’ll be given two options: receive security codes via a text message to your phone, or use a mobile app. You’ll first be prompted to enter your current password, for security reasons.

Dropbox login security