You can set up your device to prevent other people from using it if it's been reset to factory settings without your permission. For example, if your device is lost, stolen, or wiped, only someone with your Google account or screen lock information can use the device.
If your device is running Android 5.1 or higher, all you need to make sure your device is protected is:
Set a screen lock: If your device is lost or stolen but you have a screen lock set, the device can't be erased using the Settings menu unless your screen is unlocked.If your device is stolen and you don't have a screen lock set up, you can remotely lock it using Android Device Manager. You'll need to have your Google account added to your device, and your device will need to be turned on and connected to the Internet.
Add your Google account on your device: If your device is wiped but you have your Google account on it, the device can't finish the setup process until your Google account information is entered again.
Important: If you reset your Google account password and need to do a factory reset, you need to wait 72 hours after changing your password to reset your device. For security purposes, you can't use an account if the password was changed within 72 hours to set up the device after reset.
To turn off device protection, remove your Google account from your device. If you have Developer options enabled on your device.
Verify your ownership after factory reset
Since your device is protected, you'll need to either unlock your screen or enter your Google account password if you need to do a factory reset. This ensures that you or someone you trust is doing the reset.
Expect to unlock your screen or enter Google account information if you:
Erase your device's data using the Settings menu: You'll be asked to enter your screen lock before using Settings > General tab > Backup & reset.
Reset your device in Recovery mode: If you reset your device using the recovery menu, you need to enter a Google username and password associated with the device during the setup process. You need to be connected to the Internet to completely set up and use the device after reset.
Remotely reset your device with Android Device Manager: If you remotely reset your device using Android Device Manager, you need to enter a Google username and password that has been associated with the device during the setup process. You need to be connected to the Internet to completely set up and use the device after reset.
Important: You can enter information for any Google account that has been added to the device. If you can't provide this information during the setup process, you won't be able to use the device at all after factory reset.
Source: 6172890 060115