a backdoor is often a way to "break into" a system. its often left in by programmers, so where there "dumb administrators" forget there password to there multi-billion dollar computer infrastructural we can fix it.
However, this backdoor was left in for unusual reasons, as the password on your phone doesn't actually protect it, if you hook it up to a PC you can easily rip all the data off...but thats just because apple doesn't understand how to encrypt.
On a phone, when you type in the phone number your sending a code threw it...in this case ### DISCONNECT ...by doing so the phone assumes you are a systems admin, for knowing the magical backdoor.
Other phones have systems like this, mostly to get data on what towers your connected too...raw geo code data...
The blackberry system also had a fatal fault where a backdoor was well known.
So anyways back to what it does, because it assumes your a systems admin, it allows you access to the phone...photos...etc.
