To enable Two-Step verification in Dropbox, which is similar to 2-Step verification in Google, follow these steps.
1. Go to Dropbox account and go to "Security" settings.
2. Under "My Devices" section, unlink all the devices you have currently. You can link it later after you follow these steps.
3. Under the same Dropbox "Security" settings, go to "Account Sign in" and enable Two-step verification.
4. Dropbox will provide a special barcode like the picture below to add this 2-Step verification. This step will help you add it to the Google Authenticator app.
5. Download Google Authenticator app from either Google Play (Android link) or iTunes (iOS link). You can also use Amazon Authenticator app or Windows Phone 7 app.
6. Once you add the Dropbox account in Authenticator, it provide a time stamped six digit numbers, which you need to log on to your Dropbox account besides your password.
7. Download the latest Dropbox version (you don't have to uninstall your previous installations):
Windows: http://dl-web.dropbox.com/u/17/Dropbox%201.5.12.exe
Mac OS X: http://dl-web.dropbox.com/u/17/Dropbox%201.5.12.dmg
Linux x86_64: http://dl-web.dropbox.com/u/17/dropbox-lnx.x86_64-1.5.12.tar.gz
Linux x86: http://dl-web.dropbox.com/u/17/dropbox-lnx.x86-1.5.12.tar.gz
8. After you run the installation and open Dropbox, you will find that after entering the password, you will be asked to enter a six digit number.
9. Open the authenticator and enter the numbers in the Dropbox dialog box.
10. With these steps you have linked the device (computer, smartphone or tablets) to your Dropbox account. You should do the same for each device from steps 8 and 9.
The 2-step verification is a must have for both Dropbox as well as Google accounts. It is a minor convenience entering too many numbers but is worth it compared to a total breach of your files.
Via Digital Inspiration.