You can link your account to GameCenter (iOS) and Google Play (Android) to back-up your save. Simply be signed into GameCenter or Google Play while playing G.I. Joe: War on Cobra and your save will automatically be linked. Doing this will also allow you to play the same account on multiple iOS or Android devices, respectively.

Also, you can sign in to your Facebook account from the Player Profile in game which will also allow you to link your save to your Facebook account. Doing this will also allow you to play the same account on multiple different os devices, such as on an iOS device and an Android device.