It is highly recommended that all users should enable two-step verification to keep their data safe. Enable Dropbox two-step verification Enabling two-step verification is quite simple. Sign in to the Dropbox website, click on your name from the upper-right of the page, and then, click “Settings”.
Choose “Security” tab and under the “Account sign in” section, next to Two-step verification click “change” (for security reasons, you’ll be asked to re-enter your password).
To receive security code via SMS: Select “Use text messages” in the two-step verification set up and enter your phone number. You’ll be sent a security code by SMS. Verify your phone number and enable two-step verification by entering this code when prompted. Using a mobile authenticator app: You can use mobile authenticator app (available for iOS, Android, Blackberry and Windows Phone 7) to signing in to your Dropbox account. You can use Google Authenticator (Android/iPhone/BlackBerry) or Authenticator (Windows Phone 7) for this purpose. To use one of these mobile apps, select “Use a mobile app” during the two-step verification setup. You can choose to either “scan the barcode” (if your app supports it) or click “enter your secret key manually” to be given a secret key you can type into the app.
Once your app is configured, you’ll need to enter a security code generated by the authenticator app to verify setup and enable two-step verification. Note: Most apps will generate security codes even when cellular or data service is not available. So, it is useful when you traveling or where coverage is unreliable. [Via]