You could be using a jailbroken iPhone containing malicious software that spies on your every move and you wouldn’t even know it.

It might be unlikely, but it happens, and you should be aware of it — especially if you buy used devices. Fortunately, you can now get a simple app that tells you in an instant whether your iPhone or iPad has been hacked.

Jailbreakers got an unexpected present last week when a relatively unknown hacker group released a jailbreak for iOS 7.1.1. Called “Pangu,” the jailbreak package was later determined to be safe besides a shady pirate app store installed alongside the program.

But the Pangu jailbreak isn’t all that it appears. The methods the jailbreak uses to hack your device were stolen.

If you’ve thought about developing apps and tweaks for Apple’s iOS devices, but the idea of the company’s App Store approval process puts you off, then maybe it’s time to avoid that with The iOS Hacker’s Handbook. Written by a team of Mac and iOS security experts — including some prominent members of the jailbreaking community — this book promises to teach you all about the vulnerabilities and exploits in the iOS firmware.

It took the iPhone Dev-Team less than 24 hours to successfully perform a tethered jailbreak of the first iOS 5 beta, but hopes that an untethered jailbreak would be developed before iOS 5 goes public later this year have now been crushed.