According to EC Council" A bootrom exploit is a jailbreak that allows user-level access and iboot-level access. The bootrom jailbreak differs from the iboot exploit jailbreak in that the bootrom jail break exploit provides greater system level access to the attacker and the immediate follow-on exploit capability is more dangerous for the target. For example bottom exploit jailbreaks provide low-level authentication access to the filesystem and NOR access. A bootrom exploitation provides the attacker with a hole in the application to completely disregard signature checks. These exploit jailbreaks cannot be fixed by Apple. An iboot exploit jailbreak however, can be semi-tethered and can be used to allow custom firmware to enable additional follow on jailbreaking. An iboot exploit always lowers iOS controls, but the access level provided is not as damgerous as the access provided by that of a bootrom exploit jailbreak. An iboot exploit CAN be patched by Apple. This is one of the key differences.