If you are using Dropbox as the default cloud service on your Android device, you may want to set a password for Dropbox to increase security. Passcode lock can be set by doing as follows
1. Open "Dropbox" and go to "Settings" (On Samsung devices, you need to press Menu button to enter the "Settings")
2. Tap "Passcode Lock"
3. Tap "Turn passcode on" to set a password
4. Enter your passcode and re-enter to confirm it
5. Passcode is set, and you need to enter the password to be able to use Dropbox
6. To change the Dropbox passcode, tap "Change passcode". (You need to remember your Old passcode)
** Note that, there is an "Erase Data" option, which erases all Dropbox data from your device after 10 failed passcode attempts