How to Detect OS Remount in Android Apps

Last updated December 18, 2023 by Appdome

Learn to Detect OS Remount in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is OS Remount?

In Android, OS Remount is used for changing the read/write permissions of the device’s file system. By default, Android mounts the file system as read-only to prevent accidental modification or deletion of critical system files. Nevertheless, in certain situations, you may want to use OS Remount for modifying or updating system files, such as when applying a software update or installing a custom ROM. Appdome’s Detect OS Remount protection ensures that OS remounts cannot be used for malicious reasons.

Why Should Developer Prevent OS Remount?

Preventing the file system from remounting on an Android device may be necessary in certain situations, such as when you want to prevent unauthorized changes to system files, or when you want to enforce a higher level of security on the device.
Malware can abuse the remount feature and potentially lead to various security threats, such as:
  • Data theft
    Attackers can use the remount feature to modify an Android device’s system files and steal sensitive information such as passwords and credit card numbers.
  • Remote access
    By injecting malware into the system files of an Android device, attackers can gain remote access and control of the device. By gaining remote control, attackers can perform malicious actions such as installing additional malware or stealing data.
  • Rooting the device
    If attackers gain access to the file system of an Android device, they can use the remount feature to gain root access. With root access, attackers have complete control over the device and can perform a variety of malicious actions.

Prerequisites for Using Detect OS Remount:

To use Appdome’s mobile app security build system to Detect OS Remount , you’ll need:

Detect OS Remount on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Detect OS Remount without an SDK or gateway:

  1. Upload the Mobile App to Appdome.

    1. Upload an app to Appdome’s Mobile App Security Build System

    2. Upload Method: Appdome Console or DEV-API
    3. Android Formats: .apk or .aab
    4. Detect OS Remount Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
  2. Build the feature: Detect OS Remount.

    1. Building Detect OS Remount by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Detect OS Remount feature as shown below:
      2. fusion set that contains Detect OS Remount

        Figure 1: Fusion Set that will contain the Detect OS Remount feature
        Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required).

      3. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Detect OS Remount feature via Appdome Console, to add the Detect OS Remount feature to this Fusion Set.

      4. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set, as shown in Figure 1 above, and get the Fusion Set ID from the Fusion Set Detail Summary (as shown below): fusion Set Detail Summary image

        Figure 2: Fusion Set Detail Summary
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      5. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, App Center, Jenkins, Travis, Team City, Cirlce CI or other system:
        1. Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
        2. Look for sample APIs in Appdome’s GitHub Repository
    2. Building the Detect OS Remount feature via Appdome Console

      To build the Detect OS Remount protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Anti Fraud Tab > Mobile Malware Prevention section.
      2. When you select the Detect OS Remount you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Detect OS Remount

        Fusion Set applied Detect OS Remount

        Figure 4: Fusion Set that displays the newly added Detect OS Remount protection

      3. Select the Threat-Event™ in-app mobile Threat Defense and Intelligence policy for Detect OS Remount:
        1. Threat-Events™ OFF > In-App Defense

          If the Threat-Events™ setting is cleared (not selected). Appdome will detect and defend the user and app by enforcing Detect OS Remount.

        2. Threat-Events™ ON > In-App Detection

          When this setting is used, Appdome detects OS remount and passes Appdome’s Threat-Event™ attack intelligence to the app’s business logic for processing, enforcement, and user notification. For more information on consuming and using Appdome Threat-Events™ in the app, see section Using Threat-Events™ for Detect OS Remount Intelligence and Control in Mobile Apps.

        3. Threat-Events™ ON > In-App Defense

          When this setting is used, Appdome detects and defends against OS Remount (same as Appdome Enforce) and passes Appdome’s Threat-Event™ attack intelligence the app’s business logic for processing. For more information on consuming and using Appdome Threat-Events™ in the app, see section Using Threat-Events™ for Detect OS Remount Intelligence and Control in Mobile Apps.

      4. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
    Congratulations!  The Detect OS Remount protection is now added to the mobile app
  3. Certify the Detect OS Remount feature in Android Apps.

    After building Detect OS Remount, Appdome generates a Certified Secure™ certificate to guarantee that the Detect OS Remount protection has been added and is protecting the app. To verify that the Detect OS Remount protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below: Detect OS Remount shown in Certificate secure

    Figure 5: Certified Secure™ certificate

    Each Certified Secure™ certificate provides DevOps and DevSecOps organizations the entire workflow summary, audit trail of each build, and proof of protection that Detect OS Remount has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Detect OS Remount and other mobile app security features are in each build of the mobile app

Using Threat-Events™ for OS Remount Intelligence and Control in Android Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when OS Remount is detected. To consume and use Threat-Events™ for OS Remount in Android Apps, use registerReceiver in the Application OnCreate, and the code samples for Threat-Events™ for OS Remount shown below.

The specifications and options for Threat-Events™ for OS Remount are:

Threat-Event™ Elements Detect OS Remount Method Detail
Appdome Feature Name Detect OS Remount
Threat-Event Mode
OFF, IN-APP DEFENSE Appdome detects, defends and notifies user (standard OS dialog) using customizable messaging.
ON, IN-APP DETECTION Appdome detects the attack or threat and passes the event in a standard format to the app for processing (app chooses how and when to enforce).
ON, IN-APP DEFENSE Uses Appdome Enforce mode for any attack or threat and passes the event in a standard format to the app for processing (gather intel on attacks and threats without losing any protection).
Certified Secure™ Threat Event Check
Visible in ThreatScope™
Developer Parameters for Detecting OS Remount Threat-Event™
Threat-Event NAME RewritableRoot
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF 554
Threat-Event SCORE
currentThreatEventScore Current Threat-Event score
threatEventsScore Total Threat-events score
Threat-Event Context Keys
message Message displayed for the user on event
externalID The external ID of the event which can be listened via Threat Events
osVersion OS version of the current device
deviceModel Current device model
deviceManufacturer The manufacturer of the current device
fusedAppToken The task ID of the Appdome fusion of the currently running app
kernelInfo Info about the kernel: system name, node name, release, version and machine.
carrierPlmn PLMN of the device
deviceID Current device ID
reasonCode Reason code of the occured event
buildDate Appdome fusion date of the current application
devicePlatform OS name of the current device
carrierName Carrier name of the current device
updatedOSVersion Is the OS version up to date
deviceBrand Brand of the device
deviceBoard Board of the device
buildUser Build user
buildHost Build host
sdkVersion Sdk version
timeZone Time zone
deviceFaceDown Is the device face down
locationLong Location long
locationLat Location lat
locationState Location state
wifiSsid Wifi SSID
wifiSsidPermissionStatus Wifi SSID permission status

With Threat-Events™ enabled (turned ON), Android developers can get detailed attack intelligence and granular defense control in Android applications and create amazing user experiences for all mobile end users when OS Remount is detected.

The following is a code sample for native Android apps, which uses all values in the specification above for Detect OS Remount:


Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Detect OS Remount. There is no SDK and no library to code or implement in the app and no gateway to deploy in your network. All protections are built into each app and the resulting app is self-defending and self-protecting.

Releasing and Publishing Mobile Apps with Detect OS Remount

After successfully securing your app by using Appdome, there are several available options to complete your project, depending on your app lifecycle or workflow. These include:

Related Articles:

If you have any questions, please send them our way at support.appdome.com or via the chat window on the Appdome platform.

Thank you!

Thanks for visiting Appdome! Our mission is to secure every app on the planet by making mobile app security easy. We hope we’re living up to the mission with your project.

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