Android’s Stagefright bug – phone vendors taken with their pants down

Security & Privacy

You have all heard the classic mantra of computer security: use common sense, patch your system and install antivirus. That is still excellent advice, but the world is changing. We used to repeat that mantra over and over to the end users. Now we are entering a new era where we have to stress the importance of updates to manufacturers. We did recently write about how Chrysler reacted fairly quickly to stop Jeeps from being controlled remotely. They made a new firmware version for the vehicles, but didn’t have a good channel to distribute the update. Stagefright on Android demonstrates a similar problem, but potentially far more widespread.

Let’s first take a look at Stagefright. What is it really? Stagefright is the name of a module deep inside the Android system. This module is responsible for interpreting video files and playing them on the device. The Stagefright bug is a vulnerability that allows and attacker to take over the system with specially crafted video content. Stagefright is used to automatically create previews of content received through many channels. This is what makes the Stagefright bug really bad. Anyone who can send you a message containing video can potentially break into your Android device without any actions from you. You can use common sense and not open fishy mail attachments, but that doesn’t work here. Stagefright takes a look at inbound content automatically in many cases so common sense won’t help.

Even worse. There’s not much we can do about it, except wait for a patch from the operator or phone vendor. And many users will be waiting in vain. This is because of how the Android system is developed and licensed. Google is maintaining the core Linux-based system and releasing it under an open license. Phone vendors are using Android, but often not as it comes straight from Google. They try to differentiate and modifies Android to their liking. Google reacted quickly and made a fix for the Stagefright bug. This fix will be distributed to their own Nexus-smartphones soon. But it may not be that simple for the other vendors. They need to verify that the patch is compatible with their customizations, and releasing it to their customers may be a lengthy process.

If they even want to patch handsets. Some vendors seems to see products in the cheap smartphone segment as disposable goods. They are not supposed to be long-lived and post-sale maintenance is just a cost. Providing updates and patches would just postpone replacement of the phone, and that’s not in the vendor’s interest. This attitude explains why several Android vendors have very poor processes and systems for sending out updates. Many phones will never be patched.

Let’s put this into perspective. Android is the most widespread operating system on this planet. 48 % of the devices shipped in 2014 were Androids (Gartner). And that includes both phones, tablets, laptops and desktop computers. There’s over 1 billion active Android devices (Google’s device activation data). Most of them are vulnerable to Stagefright and many of them will never receive a patch. This is big!

Let’s however keep in mind that there is no widespread malware utilizing this vulnerability at the time of writing. But all the ingredients needed to make a massive and harmful worm outbreak are there. Also remember that the bug has existed in Android for over five years, but not been publically known until now. It is perfectly possible that intelligence agencies are utilizing it silently for their own purposes.

But can we do anything to protect us? That’s the hard question. This is not intended to be a comprehensive guide, but it is however possible to give some simple advice. You can stop worrying if you have a really old device with an Android version lower than 2.2. It’s not vulnerable. Google Nexus devices will be patched soon. A patch has also been released for devices with the CyanogenMod system. The privacy-optimized BlackPhone is naturally a fast-mover in cases like this.

Other devices? It’s probably best to just google for “Stagefright” and the model or vendor name of your device. Look for two things. Information about if and when your device will receive an update and for instructions about how to tweak settings to mitigate the threat. Here’s an example.

 

Safe surfing,
Micke

Image by Rob Bulmahn under CC BY 2.0

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