is the process of removing hardware restrictions imposed by iOS, Apple’s operating system, on devices running it through the use of software exploits; such devices include the iPhone, iPod touch, iPad, and second-generation Apple TV. Jailbreaking permits root access to the iOS file system and manager, allowing the download of additional applications, extensions, and themes that are unavailable through the official Apple App Store. Jailbreaking is a form of privilege escalation, and the term has been used to describe privilege escalation on devices by other manufacturers as well. The name refers to breaking the device out of its “jail”, which is a technical term used in Unix-style systems, for example in the term “FreeBSD jail”. A jailbroken iPhone, iPod touch, or iPad running iOS can still use the App Store, iTunes, and other normal functions, such as making telephone calls.
Restoring a device with iTunes removes the jailbreak
Reasons for jailbreaking
One of the reasons for jailbreaking is to expand the feature set limited by Apple and its App Store. Apple checks apps for compliance with its iOS Developer Program License Agreement before accepting them for distribution in the App Store. However, their reasons for banning apps are not limited to safety and security and may be regarded as arbitrary and capricious., To access banned apps, users rely on jailbreaking to circumvent Apple’s censorship of content and features. Jailbreaking permits the downloading of programs not approved by Apple, such as customization apps used to change the user Interface.
Since software programs available through Cydia are not required to adhere to App Store guidelines, many of them are not typical self-contained apps but instead are extensions and customizations for iOS and other apps. Users install these programs for purposes including personalization and customization of the interface by tweaks developed by developers such as Surinex and such, adding desired features and fixing annoyances, and making development work on the device easier by providing access to the filesystem and command-line tools. Many Chinese iOS device owners also jailbreak their phones to install third-party Chinese character input systems because they are easier to use than Apple’s
Cydia /sɪˈdi.ə/ is a software application for iOS that enables a user to find and install software packages on jailbroken iOS Apple devices such as the iPhone, the iPod Touch, and the iPad. It also refers to digital distribution platform for software on iOS accessed through Cydia software Most of the software packages available through Cydia are free, but some require purchasing. Cydia is developed by Jay Freeman (also called “saurik”) and his company, SaurikIT. The name “Cydia” is an allusion to the Codling Moth, with a scientific name of Cydia, which is the proverbial “worm in the apple.”
On iPhones the installation of consumer software is generally restricted to installation through the App Store. Jailbreaking therefore allows the installation of pirated applications. It has been suggested that a major motivation for Apple to prevent jailbreaking is to protect the income of its App Store, including third-party developers and allow the buildup of a sustainable market for third-party software
Types of jailbreaks
When a device is booting, it loads Apple’s own kernel initially. The device must then be exploited and have the kernel patched each time it is turned on.
An “untethered” jailbreak has the property that if the user turns the device off and back on, the device will start up completely, and the kernel will be patched without the help of a computer – thus enabling the user to boot without the need to use a computer. These jailbreaks are harder to make and take a lot of reverse engineering and years of experience.
With a “tethered” jailbreak, a computer is needed to turn the device on each time it is rebooted. If the device starts back up on its own, it will no longer have a patched kernel, and it may get stuck in a partially started state. By using a computer, the phone is essentially “re-jailbroken” (using the “boot tethered” feature of a jailbreaking tool) each time it is turned on. With a tethered jailbreak, you can still restart SpringBoard (“respring”) on the device without needing to reboot.
There is also “semi-tethered” solution, which means that when the device boots, it will no longer have a patched kernel (so it will not be able to run modified code), but it will still be usable for normal functions such as making phone calls, or texting. To use any features that require running modified code, the user must start the device with the help of the jailbreaking tool in order for it to start with a patched kernel (jailbroken).