Using the Sully fuzzing framework, the researchers have developed a way to identify flaws in SMS systems in mobile devices. Fuzzing is a form of automated software testing that involves entering random or unexpected data. Crashes or unexpected behavior arising from such input can then be analyzed as a potential vulnerability.
"Until now most of the SMS related security issues have been found by accident," state Miller and Mulliner in a paper that describes their approach. This, they explain, is because sending SMS messages costs money and because lack of access to source code for SMS implementations has meant hunting for bugs by trial and error.
The two researchers created a layer, called the injector, just above the bottom of the telephony stack that performs a man-in-the-middle attack by intercepting communication between a mobile device's modem and multiplexer.
The pair state that they found multiple SMS vulnerabilities on Android and iPhone systems and are still working on Windows Mobile systems.
In iPhone OS 2.2 and 2.2.1, they were able to crash the iPhone's SpringBoard window management application and the iPhone's CommCenter, which manages iPhone connectivity.
"This bug can be utilized for a serious denial-of-service attack since the victim can be effectively barred from making and receiving phone calls," the researchers claim.
They found a similar bug that affects Android OS 1.0, 1.1, and 1.5. "The bug is similar to the second iPhone bug in the way that it kills the telephony process (com.android.phone) and thus kicks the Android device from the mobile phone network," the pair state in their paper. "On Android the bug is a little more interesting since it will permanently kick the target device off the network if the SIM card residing in the phone has a PIN set."
Apple did not respond to a request to confirm reports that it is working on a fix for the iPhone vulnerabilities.
Google confirmed that the Android issue has been patched.
Miller and Mulliner are scheduled to present on Thursday, from 11:15 A.M. to 12:30 P.M., in the Milano Ballroom at Caesar's Palace in Las Vegas, where Black Hat is being held.
Black Hat is owned by TechWeb, which also publishes InformationWeek.
Update: Article updated to reflect Google's comment.
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