A
jailbreak is the act or tool used to perform the act of breaking out of a
chroot or
jail in
UNIX-like operating systems
[2] or bypassing
digital rights management (DRM). In the former case, it allows the user to see files outside of the
filesystem that the administrator intends to make available to the application or user in question. In the context of DRM, this allows the user to run arbitrarily defined code on devices with DRM as well as break out of chroot-like restrictions. The term originated with the
iPhone/
iOS jailbreaking community and has also been used as a term for
PlayStation Portable hacking; these devices have repeatedly been subject to jailbreaks, allowing the execution of arbitrary code, and sometimes have had those jailbreaks disabled by vendor updates.
iOS systems including the
iPhone,
iPad, and
iPod touch have been subject to
iOS jailbreaking efforts since they were released, and continuing with each firmware update.
[3][4] iOS jailbreaking tools include the option to install
Cydia, a third-party alternative to the
App Store, as a way to find and install system tweaks and binaries. To prevent iOS jailbreaking, Apple has made the device
boot ROM execute checks for
SHSH blobs in order to disallow uploads of custom kernels and prevent software downgrades to earlier, jailbreakable firmwares. In an "untethered" jailbreak, the iBoot environment is changed to execute a boot ROM exploit and allow submission of a patched low level bootloader or hack the kernel to submit the jailbroken kernel after the SHSH check.
A similar method of jailbreaking exists for
S60 Platform smartphones, which involves installing
softmod-style patches which involves patching certain ROM files while loaded in RAM
[5][6] or edited firmware (similar to the M33 hacked firmware used for the
PlayStation Portable)
[7] to circumvent restrictions on
unsigned code.
Nokia has since issued updates to curb unauthorised jailbreaking, in a manner similar to Apple.
In the case of gaming consoles, jailbreaking is often used to execute
homebrew games. In 2011,
Sony, with assistance from law firm
Kilpatrick Stockton, sued 21-year-old
George Hotz and associates of the group fail0verflow for jailbreaking the
PlayStation 3 (see
Sony Computer Entertainment America v. George Hotz and
PlayStation Jailbreak).