A recently disclosed flaw in iOS 8 dubbed "No iOS Zone" allows an attacker to create a WiFi hot spot that will cause iOS devices to become unstable, crash, and reboot, even when in offline mode. Adi Sharabani and Yair Amit of Skycure are working with Apple for a fix; but, for now, the only workaround is to simply not be in range of such a malicious network.
http://mobile.slashdot.org/story/15/...evices-in-area