An iPhone 3GS showing the Cydia package manager on its screen. Photo: Kgw1226, CC BY-SA 4.0, via Wikimedia Commons.
In March 2012 this was our most clicked menu item: "Jailbreak 5.1". Apple had just released iOS 5.1, many people had updated by accident, and they wanted their tweaks back. The answer was a tool called redsn0w, with a catch.
redsn0w and the iPhone Dev Team
redsn0w was a desktop tool from the iPhone Dev Team, a group of researchers that included MuscleNerd and planetbeing. It relied on the limera1n bootrom exploit, a hardware-level flaw in A4 and older chips, so it worked on the iPhone 4, iPhone 3GS, the first iPad and the third and fourth generation iPod touch. Newer A5 devices such as the iPhone 4S were not covered.
Within days of iOS 5.1 shipping, redsn0w was updated to jailbreak it, but only in tethered form.
Tethered: the dreaded word
A tethered jailbreak meant the phone could not boot into its jailbroken state on its own. Every time it restarted, whether from a crash, a flat battery or a deliberate reboot, it had to be connected to a computer and booted with the tool. If you were away from your computer, a dead battery could leave you with a phone that did not work properly until you got home.
The Dev Team itself warned people to avoid tethered jailbreaks unless they understood the consequences. Some owners of the old-bootrom iPhone 3GS were luckier: on that hardware the same release was untethered.
How it ended
In May 2012 Absinthe 2.0 delivered an untethered jailbreak for iOS 5.1.1 on almost every device, and the tethered workaround was quickly forgotten. We tell that part of the story in our article on Absinthe and the iPhone 4S.
The lesson that stayed
The iOS 5.1 episode taught a generation of users to stop and think before pressing "Update". That habit has a downside. Holding back updates for the sake of a jailbreak means keeping known security holes open, and today that is a poor trade for anyone who uses their phone for banking, shopping or betting accounts. Our guide to phone security for betting accounts explains why up-to-date iOS is the first line of defence.
A note for collectors: if you still have an old iPhone 4 or 3GS in a drawer, it is a lovely piece of history. Treat it as a museum piece rather than a daily phone, because its software has not received security updates for many years.