How to Detect Unknown Sources, Protect Android Apps

Last updated August 11, 2022 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.

Detecting Unknown Sources on Android apps by 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
  2. Build the Protection: 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. How: Toggle (turn ON) Detect Unknown Sources, as shown below. Detect Unknown Sources option

        Figure 3: Detect Unknown Sources option

      3. 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

      4. 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.

      5. 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
  3. Certify the Detect Unknown Sources feature in Android Apps.

    After building Detect Unknown Sources, Appdome generates a Certified Secure™ certificate to guarantee that the Detect Unknown Sources protection has been added and is protecting the app. To verify that the Detect Unknown Sources protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below: Detect Unknown Sources 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 Unknown Sources has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Detect Unknown Sources and other mobile app security features are in each build of 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 DETECTON 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
messageMessage displayed for the user on event
externalIDThe external ID of the event which can be listened via Threat Events
osVersionOS version of the current device
deviceModelCurrent device model
deviceManufacturerThe manufacturer of the current device
fusedAppTokenThe task ID of the Appdome fusion of the currently running app
kernelInfoInfo about the kernel: system name, node name, release, version and machine.
carrierPlmnPLMN of the device
deviceIDCurrent device ID
reasonCodeReason code of the occured event
buildDateAppdome fusion date of the current application
devicePlatformOS name of the current device
carrierNameCarrier name of the current device
updatedOSVersionIs the OS version up to date
deviceBrandBrand of the device
deviceBoardBoard of the device
buildUserBuild user
buildHostBuild host
sdkVersionSdk version
timeZoneTime zone
deviceFaceDownIs the device face down
locationLongLocation long
locationLatLocation lat
locationStateLocation state
wifiSsidWifi SSID
wifiSsidPermissionStatusWifi 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:

Prerequisites to Using Detect Unknown Sources:

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

Using Appdome, there are no development or coding prerequisites to build secured 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:

All apps protected by Appdome are fully compatible with any public app store, including Apple App Store, Google Play, Huawei App Gallery and more.

Protections Similar to Detect Unknown Sources

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!

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