"Apple iOS is widely viewed as the most trusted mobile operating system out there". This means of all the processes running behind iOS, it is the very first to start up when an iPhone is turned on.
The unmasking of the iPhone code may allow hackers, known as jailbreakers, to find a way to break into a victim's iPhone and decrypt their data. It also loads and verifies that information is properly signed by Apple when your phone is booting up.
He continued: "iBoot is the one component Apple has been holding on to, still encrypting its 64-bit image. now it's wide open in source code form". Essentially, it is like the BIOS code found in PCs.
Apple's iOS source code has been a closely-guarded secret for some time, and many have argued that the company's closed ecosystem is what contributes the most to its strong security.
However, there are iPhone and iPad users who should be anxious - people who are still using iOS 9.
Apple has been particularly cautious about releasing code to the public: only certain parts of its operating system are open-source, and the company runs a bounty program which pays $200,000 to anyone who finds a bug in its programming.
However, Jonathan Levin, who wrote a series of books on iOS and Mac OSX internals, has described it as a "big deal" and the "biggest leak in history".
Apple directed Github to remove the code since all codes are kept private to ensure consumer's privacy.
The code leaked onto GitHub claims to be designed for iOS 9 but much of it is likely to be found in iOS 11, making the leak potentially risky to Apple's mobile software. The code's widespread availability on GitHub means that hackers likely already have their hands on it.
Levin said the code appears to be the real iBoot code because it aligns with code he reverse engineered himself.