Exploit:Android/Masterkey

Classification

Malware

Exploit

Android

Aliases for public viewing

Summary

Exploit:Android/Masterkey identifies code designed to exploit a known vulnerability in the way the Android operation system verifies the authenticity of an app.

Automatic action

Once the scan is complete, the F-Secure security product will ask if you want to uninstall the file, move it to the quarantine or keep it installed on your device.

Vulnerability Protection

The vulnerability leveraged by the exploit is application or platform specific; in other words, a specific program (or even a specific version of a particular program) must be installed in order for the exploit to be effective.

To prevent exploitation of such vulnerabilities, please refer to the application or device vendor for the latest updates and additional advice.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

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Submit a sample

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Technical Details

From the F-Secure Mobile Threat Report Q3 2013:

In July [2013], security researchers publicly announced the discovery of a vulnerability in cryptographic signature verification for Android apps that, if exploited, would allow an attacker to modify a legitimate app’s code without affecting its cryptographic signature - essentially keeping the tampering from being detected during verification. Shortly after the announcement, researchers were able to find samples of such modified apps being distributed.

Google was reportedly notified of the "Masterkey" issue earlier in the year, and at the time of the announcement had fixed the issue in the Android open source codebase. Users would however still need to wait for a firmware update from their device manufacturer in order to receive the patched code.