Apple's screw-up leaves tethered iPhones easily crackable
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So the team then reverse-engineered the iOS word list used for password generation, using "static and dynamic analysis," tools like GNU Debugger, and by manually going through the ARM disassembly of the relevant iOS frameworks. They found Apple uses English-language words of between four and six letters from a dictionary copyrighted by Lernout & Hauspie Speech Products.
"Only 1,842 different entries of that dictionary are taken into consideration," the paper states. "Consequently, any default password used within an arbitrary iOS mobile hotspot, is based on one of these 1,842 different words. This fact reduced the search space of our initial brute force attack by more than 96% and thus increased the overall cracking speed significantly."
In addition, the selection of words picked for passwords was skewed. "Suave" was used 0.08 per cent of the time, "subbed" cropped up 0.76 per cent and "head" 0.53 per cent – ten times the frequency they should have had under a random pick. By frontloading these selections into any attack code, the chances of cracking the system quickly are greatly increased.
The team also decided to upgrade their hardware to bring down search times and built a box with four AMD Radeon HD 7970 units that could burn through 390,000 guesses per second. This cut the time to crack automatically generated passwords down to 24 seconds, or 52 using a single AMD Radeon HD 6990 GPU. Users should specify their own the team recommends.
http://www.theregister.co.uk/2013/06/18/iospoor_passwords_crackable_24_seconds/