Stagefright Exploit

The InfoSec community has seen a rise in attention grabbing names for security vulnerabilities over the last couple years like Heartbleed, Freak, Shellshock, and now the latest android vulnerability Stagefright. The Stagefright exploit is different though, its name is derived from the media engine baked into android OS since version 2.2. The Stagefright engine is built into the application framework of android making it a part of your android OS no matter what country you live in, wireless carrier you use, or what brand of phone you buy. It is estimated there are 950 million devices vulnerable to a Stagefright attack.

The most alarming issue about this exploit is that it can be executed with no end-user interaction. An attacker simply has to send an mms message with malicious code written into a video and the device automatically begins to process the code, setting the attack in motion. Further complicating matters is most manufacturers default settings which are set to auto-retrieve mms messages. The user may not even know they were attacked because after the exploit gains root access of the phone the message is deleted but the malicious code stays.

The Stagefright media engine runs with system privileges on roughly 50 percent of the affected devices making it easy to gain root access to the device. Gaining root access on an android phone is the holy grail of exploits and the damage that can be caused is only limited by the attacker’s imagination.

Android is an open source OS which some might say makes it more secure while others would argue the opposite. The security architecture built into system applications in android take the sandbox approach. Most system apps are designed to be contained within themselves so attacks like the Stagefright exploit are not possible. This brings up the question of why the Stagefright engine has access to the internet and can be executed without the user’s knowledge. The answer is the DRM (Digital Rights Management) copyright control technologies that have been implemented over the last decade have required media players to make sure the content is being played legally. The technologies used to protect the content often require media players to check in via the internet, leaving a door open for malware.

Google has already began patching its Nexus line of phones and tablets with Samsung following as well. The inherent problem with android OS is that it is segmented into thousands of different variations of devices and carriers which makes patching a security hole like this a difficult task. Carriers like AT&T and Verizon control the software updates that get pushed out to their customers further complicating the matter. If there is a silver lining in this exploit being brought forth it is that Google and Samsung are going to begin delivering monthly security updates to devices. This is a step in the right direction for mobile device security.

Here is how to protect yourself from falling victim the Stagefright exploit:

Android Kitkat – Open the messenger app and in the settings menu select “block unknown senders”

Android Lollipop – Open the messenger app and turn off Auto-Retrieve for multimedia messages.

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