How to Block Resigning and Repackaging Android Apps

Last updated May 26, 2024 by Appdome

Learn to Prevent App Repacking in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is App Repackaging?

App repacking involves hackers manipulating an app’s original code or injecting harmful code into it, subsequently repackaging this altered app for distribution. By actively preventing app repacking, you not only preserve the authenticity and originality of your app but also ensure the continuous safety and trust of your users.

To ensure your app is protected against unauthorized changes or any modification that can compromise them is critical. Some examples are:

Why Prevent App Repacking in Android Apps??

Tamper prevention against app repackaging protects your app against unwanted changes, mods, and hacks  that can negative impact or compromise your mobile business application including financial and data loss, intellectual privacy & repetitional damage. Appdome prevents all this without adding development work or time to your release cycles.  This is done by sealing your app and actively detecting modifications during initialization and at multiple other points during run-time.

Prerequisites for Using Prevent App Repacking:

To use Appdome’s mobile app security build system to Prevent App Repacking , you’ll need:

Prevent App Repacking on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Prevent App Repacking 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. Prevent App Repacking Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
  2. Build the feature: Prevent App Repacking.

    1. Building Prevent App Repacking by using Appdome’s DEV-API:

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

        Figure 1: Fusion Set that will contain the Prevent App Repacking 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 Prevent App Repacking feature via Appdome Console, to add the Prevent App Repacking 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, Circle 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 Prevent App Repacking feature via Appdome Console

      To build the Prevent App Repacking protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > ONEShield™ section.
      2. When you select the Prevent App Repacking you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Prevent App Repacking

        Fusion Set applied Prevent App Repacking

        Figure 4: Fusion Set that displays the newly added Prevent App Repacking protection

      3. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
    Congratulations!  The Prevent App Repacking protection is now added to the mobile app

Using Threat-Events™ for App Repacking Intelligence and Control in Android Apps

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

The specifications and options for Threat-Events™ for App Repacking are:

Threat-Event™ Elements Prevent App Repacking Method Detail
Appdome Feature Name Prevent App Repacking
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 Preventing App Repacking Threat-Event™
Threat-Event NAME AppIntegrityError
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF 6801
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 longitude conditioned by location permission
locationLat Location latitude conditioned by location permission
locationState Location state conditioned by location permission
wifiSsid Wifi SSID
wifiSsidPermissionStatus Wifi SSID permission status
AntampIntegrityErrorMessage Error message
data Data related to the security event
certificateSHA1 Failed certificate

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 App Repacking is detected.

The following is a code sample for native Android apps, which uses all values in the specification above for Prevent App Repacking:


Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Prevent App Repacking. 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 Prevent App Repacking

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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