How to Detect Unknown Sources, Protect Android Apps

Last updated December 6, 2023 by Appdome

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

What is Unknown Sources?

With Appdome’s “Detect Unknown Sources” feature integrated into a mobile app, the app protects itself by detecting that the Android OS feature “allow app installs from unknown sources” setting is turned ON and preventing abuse of Unknown Sources to deliver Malware.

Why Detect Unknown Sources in Android Apps?

Unknown Sources is an Android accessibility setting that allows the phone to trust and install applications from any developers, publisher or source outside of the Google Play store. Having this Android OS feature enabled can be used to trick unsuspecting users to install malware disguised as legitimate software.

Prerequisites for Using Detect Unknown Sources:

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

Detect Unknown Sources on Android apps using Appdome

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

    1. Building Detect Unknown Sources by using Appdome’s DEV-API:

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

        Figure 1: Fusion Set that will contain the Detect Unknown Sources 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 Unknown Sources feature via Appdome Console, to add the Detect Unknown Sources 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 Unknown Sources feature via Appdome Console

      To build the Detect Unknown Sources protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > OS Integrity section.
      2. When you select the Detect Unknown Sources 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 Unknown Sources

        Fusion Set applied Detect Unknown Sources

        Figure 4: Fusion Set that displays the newly added Detect Unknown Sources protection

      3. Select the Threat-Event™ in-app mobile Threat Defense and Intelligence policy for Detect Unknown Sources:
        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 Unknown Sources.

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

          When this setting is used, Appdome detects when "allow app install from unknown sources" native OS setting is enabled on the device 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 Unknown Sources Intelligence and Control in Mobile Apps.

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

          When this setting is used, Appdome detects and defends against Unknown Sources (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 Unknown Sources 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 Unknown Sources protection is now added to the mobile app

Using Threat-Events™ for Unknown Sources Intelligence and Control in Android Apps

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

The specifications and options for Threat-Events™ for Unknown Sources are:

Threat-Event™ Elements Detect Unknown Sources Method Detail
Appdome Feature Name Detect Unknown Sources
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 Unknown Sources Threat-Event™
Threat-Event NAME UnknownSourcesEnabled
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF 6701
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 Unknown Sources is detected.

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


Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Detect Unknown Sources. 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 Unknown Sources

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:

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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