Researchers have demonstrated iPhone malware that works even when the phone is fully shut down.

t turns out that the iPhone’s Bluetooth chip­ — which is key to making features like Find My work­ — has no mechanism for digitally signing or even encrypting the firmware it runs. Academics at Germany’s Technical University of Darmstadt figured out how to exploit this lack of hardening to run malicious firmware that allows the attacker to track the phone’s location or run new features when the device is turned off.

[…]

The research is the first — or at least among the first — to study the risk posed by chips running in low-power mode. Not to be confused with iOS’s low-power mode for conserving battery life, the low-power mode (LPM) in this research allows chips responsible for near-field communication, ultra wideband, and Bluetooth to run in a special mode that can remain on for 24 hours after a device is turned off.

The research is fascinating, but the attack isn’t really feasible. It requires a jailbroken phone, which is hard to pull off in an adversarial setting.

Slashdot thread.