JailbreakMe has to be hands down the easiest jailbreak method ever, but since it uses userland exploit like Spirit, it doesn’t hacktivate phones. iPhone dev and hacker named Sherif Hashim came up with a way to activate phones without having the original SIM cards but now it seems like Apple has found out about the phonebook SIM card trick and they have blocked it. And so if you activated your phone using phonebook SIM card, you will be getting the dreaded “Different SIM Detected” error on your lockscreen as shown in the screenshot below.
