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How to Ensure Malicious Android Applications Don't Use Raw Files

Android applications can use raw resources, which are files packaged with the application APK. These raw files can include XML configurations, text files, and other data. However, malicious apps can also use raw files to hide malware or perform nefarious activities. In this blog post, we'll discuss some best practices for ensuring that Android applications don't misuse raw files to pose a threat.

Check the App's Manifest File

The manifest file is an essential component of any Android application as it provides crucial metadata about the app. By analyzing the manifest file, you can identify the raw resources used by the app and their respective file paths. It's important to note that not all malicious apps will declare their raw files in the manifest; however, checking this file is still a good starting point.

Analyze the App's Code

Malware authors often use obfuscated code or packers to hide their malicious activities from casual analysis. However, you can still perform some static code analysis using tools like JADX and Dex2jar. These tools allow you to decompile the Dalvik executable (DEX) format of the Android app into Java-like code, making it easier to understand.

When analyzing the code, look for any suspicious usage of raw files:

  1. Input/output streams reading or writing to raw files without a clear purpose.
  2. File paths that are hardcoded or calculated based on system information (e.g., Environment.getDataDirectory()).
  3. Encrypted data being read from or written to raw files.

Monitor the App's Behavior

Analyzing the app's code alone might not be enough to detect all types of malware. Malicious apps may exhibit certain behaviors when running that are not apparent in the static analysis. To monitor the app's behavior, you can use tools like Android Debug Bridge (ADB) or third-party monitoring apps.

Keep an eye on the following activities:

  1. Unusual network traffic patterns, such as excessive data transfers or communicating with known malicious domains.
  2. Persistent background processes that consume significant system resources or run without user interaction.
  3. Suspicious file writes to the external storage or system directories.

Conclusion

By following these best practices, you can help ensure that Android applications don't misuse raw files for malicious purposes. It's essential to remember that no solution is foolproof, and new threats are constantly emerging. Stay informed about the latest security trends and be vigilant when installing new apps on your device.

For more information on mobile application security, consider checking out our Mobile Application Security series.

Published June, 2017