An Android master key could affect any Android device released during the past four years, representing nearly 900 million devices and 99% of the market.
That is the verdict of Bluebox Security research team, who recently discovered a vulnerability in Android’s security model.
Findings suggest the breach allows a hacker to modify APK code without breaking an application’s cryptographic signature and to turn any legitimate application into a malicious Trojan, completely unnoticed by the app store, the phone, or the end user.
"The implications are huge," says Jeff Forristal, CTO, Bluebox.
"This vulnerability, around at least since the release of Android 1.6 (codename: “Donut” ), could affect any Android phone released in the last four years - depending on the type of application, a hacker can exploit the vulnerability for anything from data theft to creation of a mobile botnet.
"While the risk to the individual and the enterprise is great, this risk is compounded when you consider applications developed by the device manufacturers (e.g. HTC, Samsung, Motorola, LG) or third-parties that work in cooperation with the device manufacturer (e.g. Cisco with AnyConnect VPN) – that are granted special elevated privileges within Android – specifically System UID access."
Forristal says installation of a Trojan application from the device manufacturer can grant the application full access to Android system and all applications (and their data) currently installed.
The application then not only has the ability to read arbitrary application data on the device (email, SMS messages, documents, etc.), retrieve all stored account & service passwords, it can essentially take over the normal functioning of the phone and control any function thereof (make arbitrary phone calls, send arbitrary SMS messages, turn on the camera, and record calls).
Finally, and most unsettling according to Forristal, is the potential for a hacker to take advantage of the always-on, always-connected, and always-moving (therefore hard-to-detect) nature of these “zombie” mobile devices to create a botnet.
How it works:
The vulnerability involves discrepancies in how Android applications are cryptographically verified & installed, allowing for APK code modification without breaking the cryptographic signature.
All Android applications contain cryptographic signatures, which Android uses to determine if the app is legitimate and to verify that the app hasn’t been tampered with or modified.
This vulnerability makes it possible to change an application’s code without affecting the cryptographic signature of the application – essentially allowing a malicious author to trick Android into believing the app is unchanged even if it has been.
Details of Android security bug 8219321 were responsibly disclosed through Bluebox Security’s close relationship with Google in February 2013.
It’s up to device manufacturers to produce and release firmware updates for mobile devices (and furthermore for users to install these updates). The availability of these updates will widely vary depending upon the manufacturer and model in question.
How to stop it:
• Device owners should be extra cautious in identifying the publisher of the app they want to download.
• Enterprises with BYOD implementations should use this news to prompt all users to update their devices, and to highlight the importance of keeping their devices updated.
• IT should see this vulnerability as another driver to move beyond just device management to focus on deep device integrity checking and securing corporate data.