Untethered jailbreaking is a persistent exploitation method that modifies the device's core boot process. It installs an exploit that automatically patches the kernel every time the device starts up. This ensures the device remains in a jailbroken state after any reboot, without requiring any connection to a computer or manual intervention from the user. The exploit is self-contained on the device and executes during the boot sequence, making it the most seamless but also the most complex type of jailbreak to achieve.

A. Tethered jailbreaking: This method requires the device to be connected to a computer each time it is rebooted to re-apply the kernel patch and boot into a jailbroken state.
B. Semi-tethered jailbreaking: The device can boot on its own, but only into a non-jailbroken state. A computer is required to re-run the exploit and re-jailbreak the device.
D. Semi-Untethered jailbreaking: The device reboots into a non-jailbroken state, but the user can re-jailbreak it by running an application on the device itself, without needing a computer.

1. Yeo

S.

Kim

H.

& Lee

H. (2017). A Survey on iOS Jailbreaking. Journal of The Korea Institute of Information Security and Cryptology

27(4)

85-98.

Page 88

Section 3.1.3: "Untethered jailbreak is a method of jailbreaking without connecting to a PC after rebooting. The exploit code is stored in the device and the kernel patch is automatically executed when booting." This directly defines the correct answer. The same section also defines tethered and semi-untethered methods

supporting the reasoning for incorrect options.

2. Zheng

X.

et al. (2013). A Survey on Security of iOS. Tsinghua Science and Technology

18(1)

84-95. https://doi.org/10.1109/TST.2013.6449404

Page 89

Section 4.1: The paper describes untethered jailbreaking as a process where "the exploit is triggered automatically during the boot process without any user interaction

" which allows the device to "reboot into a jailbroken state."

3. Enck

W. (2020). CSC 495/591: Mobile and IoT Security Courseware. North Carolina State University.

Lecture 10: iOS Security

Slide 32 ("Jailbreaking"): The lecture notes categorize jailbreaks and define "Untethered" as a method where the "Device is permanently jailbroken. Exploit automatically runs on boot." This contrasts with "Tethered" and "Semi-tethered" which require external assistance post-reboot.