Failure modes could include:
Finally, the most relevant consideration is 2FA (two factor authentication). This says that access to the device requires something-you-know and something-you-are.
Breaking into an iPhone with 2FA enabled isn’t easy. The attacker would need the password and use the owner’s finger. It won’t even work if you cut off the user’s finger because the scanner accepts only living tissue. But a spouse … hmm…
1. if you jailbreak or root any device, you’ll be screwed
2. if you install apps from untrusted places, you’ll be screwed.
3. to install apps from untrusted places, you need to explicitly allow untrusted apps on Android and on Mac OS X. On the iPhone it’s not possible.
4. to install apps from untrusted places you need to explicitly accept and approve a developer profile (enterprise). This is a multi-step procedure that asks you “are you really sure” a million times, including asking you for your passcode.
5. to install apps from untrusted places you’ll still need to explicitly aprove the app the first time you run it. “do you want to run <app> from developer <developer>?”
6. to be vulnerable via USB you need to explicitly state you do trust that computer