iCloud: Erase your device remotely
If your device is lost or stolen, you can erase the personal information (such as your contacts, email, and music) and settings on that device to prevent anyone else from seeing or using your information.
If you erase your iOS device and then find it, you can restore the information on the device using iCloud Backup (if backup was turned on before you erased it) or iTunes. For more information, see the user guide for your device in Safari bookmarks or on the Apple Support website.
To erase your device remotely, you need to have set up Find My iPhone on the device before it was lost.
Erase the information on your lost device
If you’re already signed in to a different application on icloud.com, click the iCloud button to switch applications.
Click Devices, then select the device you want to erase.
In the device’s Info window, click Erase Device.
Do one of the following:
To erase an iOS device, enter your Apple ID password, then click Erase.
To erase a Mac, enter a passcode that you’ll need to use to unlock the device if you find it (to prevent anyone but yourself from using the computer if it’s found), then follow the onscreen instructions.
When asked to type a message, you may want to indicate how to contact you if the device is found. For example, “This Mac is lost. If found, please call me at yourphonenumber.”
If the device is online, the remote erase begins within seconds (if the device is a Mac, it also restarts before it’s erased), and a confirmation email is sent to your Apple ID email address (the one you use with iCloud).
If the device is offline, the information is erased the next time it’s online.