How to Protect Android Apps from Overlay Attacks & Malware

Last updated August 11, 2022 by Appdome

Learn to Block Overlay Attacks in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What are Overlay Attacks ?

In an Overlay Attack (aka “Screen Overlay Attack” or “Clickjacking”) the attacker uses a transparent or opaque UI layer above the legitimate UI layer to trick a mobile end user into interacting with the malicious overlay before, instead of, or as the mobile end-user interacts with the legitimate UI layer. The malicious overlay can be a button, data entry field or another screen inside a mobile app, which resembles or mimics the real UI and can, for example, be covered by the malicious overlay malware that the hacker controls. Malware, fake apps, and social engineering techniques can be combined with Overlay Attacks to make the attack more believable and more effective. Examples of known and documented Overlay Attacks include Anubis, BankBot, StrandHogg, BlackRock, Cloak&Dagger, Ghimob, Ginp, and MazarBot.

Why Block Overlay Attacks in Android Apps?

Blocking Overlay Attacks is often required by the laws and regulations where the Android app is used. On top of that, Overlay Attacks are extremely dangerous attacks against any Android app in a regulated industry, such as Financial Services, Mobile Healthcare, or Mobile Retail Android apps. One of the goals of Overlay Attacks is primarily data theft or data harvesting. The reality is that all forms of critical mobile end-user data such as transactions, account, login, PII, and mobile patient data are at risk in an Overlay Attack. For example, in a mobile banking or other mobile app relying on mobile purchases or other transactions, username, password, account numbers, credit card info, transaction (e.g., ATM) pin codes, security questions, etc. can all be at risk if Overlay Attacks are not prevented or blocked.

Blocking Overlay Attacks on Android apps by Using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Block Overlay Attacks without an SDK or gateway:

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
Build the feature: Block App Overlay Attacks .
1. Building Block App Overlay Attacks by using Appdome’s DEV-API:
  1. Create and name the Fusion Set (security template) that will contain the Block App Overlay Attacks feature as shown below:
  2. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Block App Overlay Attacks feature via Appdome Console, to add the Block App Overlay Attacks feature to this Fusion Set.
  3. 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):
    
    Figure 2: Fusion Set Detail Summary
    Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).
  4. 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:
    
    Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
    
    Look for sample APIs in Appdome’s GitHub Repository
2. Building the Block App Overlay Attacks feature via Appdome Console
  
  To build the Block App Overlay Attacks protection by using Appdome Console, follow the instructions below.
  1. Where: Inside the Appdome Console, go to Build > Anti Fraud Tab > Mobile Fraud Prevention section
  2. How: Toggle (turn ON) Block App Overlay Attacks , as shown below.
    
    Figure 3: Block Overlay Attacks option
  3. When you select the Block App Overlay Attacks you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Block App Overlay Attacks
    
    Figure 4: Fusion Set that displays the newly added Block App Overlay Attacks protection
  4. Select the Threat-Event™ in-app mobile Threat Defense and Intelligence policy for Block App Overlay Attacks :
    
    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 Block Overlay Attacks .
    
    Threat-Events™ ON > In-App Detection
    When this setting is used, Appdome detects overlay attacks 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 Block App Overlay Attacks Intelligence and Control in Mobile Apps.
    
    Threat-Events™ ON > In-App Defense
    When this setting is used, Appdome detects and defends against Overlay Attacks (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 Block App Overlay Attacks Intelligence and Control in Mobile Apps.
  5. Optional Configuration with Block App Overlay Attacks :
    Prevent StrandHogg
    Prevent overlay attacks based on StrandHogg, a critical Android vulnerability.
    Trust Specified Activities Only
    Specify the class name of the activity to exclude from Overlay detection
  6. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
Congratulations! The Block App Overlay Attacks protection is now added to the mobile app
Certify the Block App Overlay Attacks feature in Android Apps.

After building Block App Overlay Attacks , Appdome generates a Certified Secure™ certificate to guarantee that the Block App Overlay Attacks protection has been added and is protecting the app. To verify that the Block App Overlay Attacks protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below:

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 Block App Overlay Attacks has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Block App Overlay Attacks and other mobile app security features are in each build of the mobile app

Using Threat-Events™ for Overlay Attacks Intelligence and Control in Android Apps

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

The specifications and options for Threat-Events™ for Overlay Attacks are:

Threat-Event™ Elements	Block Overlay Attacks Method Detail
Appdome Feature Name	Block App Overlay Attacks
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 Blocking Overlay Attacks Threat-Event™
Threat-Event NAME	OverlayDetected
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 long
locationLat	Location lat
locationState	Location state
wifiSsid	Wifi SSID
wifiSsidPermissionStatus	Wifi SSID permission status
reason	Type of overlay
data	Overlay activity path

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 Overlay Attacks are detected.

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

IntentFilter intentFilter = new IntentFilter();
                    intentFilter.addAction("OverlayDetected");
                    registerReceiver(new BroadcastReceiver() {
                            @Override
                            public void onReceive(Context context, Intent intent) {
                                String message = intent.getStringExtra("message"); // Message shown to the user
                                String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
                                String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
                                String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Current threat event score
                                String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Total threat events score
                                String variable = intent.getStringExtra("<Context Key>"); // Any other event specific context key

                                // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                            }
                        }, intentFilter);

                        
                        Java
                    
​x
 
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("OverlayDetected");
registerReceiver(new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String message = intent.getStringExtra("message"); // Message shown to the user
            String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
            String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
            String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Current threat event score
            String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Total threat events score
            String variable = intent.getStringExtra("<Context Key>"); // Any other event specific context key
​
            // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
        }
    }, intentFilter);

val intentFilter = IntentFilter()
                intentFilter.addAction("OverlayDetected")
                registerReceiver(object : BroadcastReceiver() {
                    override fun onReceive(context: Context?, intent: Intent?) {
                        var message = intent.getStringExtra("message") // Message shown to the user
                        var reasonData = intent.getStringExtra("reasonData") // Threat detection cause
                        var reasonCode = intent.getStringExtra("reasonCode") // Event reason code
                        var currentThreatEventScore = intent.getStringExtra("currentThreatEventScore") // Current threat event score
                        var threatEventsScore = intent.getStringExtra("threatEventsScore") // Total threat events score
                        var variable = intent.getStringExtra("<Context Key>") // Any other event specific context key

                        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                    }
                }, intentFilter)

                         
                        Kotlin
                    
​x
 
val intentFilter = IntentFilter()
intentFilter.addAction("OverlayDetected")
registerReceiver(object : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        var message = intent.getStringExtra("message") // Message shown to the user
        var reasonData = intent.getStringExtra("reasonData") // Threat detection cause
        var reasonCode = intent.getStringExtra("reasonCode") // Event reason code
        var currentThreatEventScore = intent.getStringExtra("currentThreatEventScore") // Current threat event score
        var threatEventsScore = intent.getStringExtra("threatEventsScore") // Total threat events score
        var variable = intent.getStringExtra("<Context Key>") // Any other event specific context key
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    }
}, intentFilter)

const { ADDevEvents } = NativeModules;
                const aDDevEvents = new NativeEventEmitter(ADDevEvents);

                function registerToDevEvent(action, callback) {
                    NativeModules.ADDevEvents.registerForDevEvent(action);
                    aDDevEvents.addListener(action, callback);
                }

                export function registerToAllEvents() {
                    registerToDevEvent(
                        "OverlayDetected",
                        (userinfo) => Alert.alert(JSON.stringify(userinfo))

                        var message = userinfo["message"] // Message shown to the user
                        var reasonData = userinfo["reasonData"] // Threat detection cause
                        var reasonCode = userinfo["reasonCode"] // Event reason code
                        var currentThreatEventScore = userinfo["currentThreatEventScore"] // Current threat event score
                        var threatEventsScore = userinfo["threatEventsScore"] // Total threat events score
                        var variable = userinfo["<Context Key>"] // Any other event specific context key

                        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                    );
                }

                     
                    React Native
                
​x
 
const { ADDevEvents } = NativeModules;
const aDDevEvents = new NativeEventEmitter(ADDevEvents);
​
function registerToDevEvent(action, callback) {
    NativeModules.ADDevEvents.registerForDevEvent(action);
    aDDevEvents.addListener(action, callback);
}
​
export function registerToAllEvents() {
    registerToDevEvent(
        "OverlayDetected",
        (userinfo) => Alert.alert(JSON.stringify(userinfo))
​
        var message = userinfo["message"] // Message shown to the user
        var reasonData = userinfo["reasonData"] // Threat detection cause
        var reasonCode = userinfo["reasonCode"] // Event reason code
        var currentThreatEventScore = userinfo["currentThreatEventScore"] // Current threat event score
        var threatEventsScore = userinfo["threatEventsScore"] // Total threat events score
        var variable = userinfo["<Context Key>"] // Any other event specific context key
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    );
}
​

RegisterReceiver(new ThreatEventReceiver(), new IntentFilter("OverlayDetected"));
                class ThreatEventReceiver : BroadcastReceiver
                {
                public override void OnReceive(Context context, Intent intent)
                {
                    String message = intent.getStringExtra("message"); // Message shown to the user
                    String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
                    String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
                    String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Current threat event score
                    String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Total threat events score
                    String variable = intent.getStringExtra("<Context Key>"); // Any other event specific context key

                    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                }
                }

                    
                    Xamarin
                
​x
 
RegisterReceiver(new ThreatEventReceiver(), new IntentFilter("OverlayDetected"));
​
class ThreatEventReceiver : BroadcastReceiver
{
  public override void OnReceive(Context context, Intent intent)
  {
    String message = intent.getStringExtra("message"); // Message shown to the user
    String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
    String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
    String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Current threat event score
    String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Total threat events score
    String variable = intent.getStringExtra("<Context Key>"); // Any other event specific context key
​
    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
  }
}

window.broadcaster.addEventListener("OverlayDetected", function(userInfo) {
        var message = userInfo.message // Message shown to the user
        var reasonData = userInfo.reasonData // Threat detection cause
        var reasonCode = userInfo.reasonCode // Event reason code
        var currentThreatEventScore = userInfo.currentThreatEventScore // Current threat event score
        var threatEventsScore = userInfo.threatEventsScore // Total threat events score
        var variable = userInfo.<Context Key> // Any other event specific context key

        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
            });

                    
                    Cordova
                
​x
 
window.broadcaster.addEventListener("OverlayDetected", function(userInfo) {
        var message = userInfo.message // Message shown to the user
        var reasonData = userInfo.reasonData // Threat detection cause
        var reasonCode = userInfo.reasonCode // Event reason code
        var currentThreatEventScore = userInfo.currentThreatEventScore // Current threat event score
        var threatEventsScore = userInfo.threatEventsScore // Total threat events score
        var variable = userInfo.<Context Key> // Any other event specific context key
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});

Prerequisites to Using Block App Overlay Attacks :

To use Appdome’s mobile app security build system to Block Overlay Attacks , you’ll need:

Appdome account (create a free Appdome account here)
A license for Block App Overlay Attacks
Mobile App (.apk or .aab For Android)
Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

Using Appdome, there are no development or coding prerequisites to build secured Apps by using Block App Overlay Attacks . 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 Block App Overlay Attacks

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:

Customizing, Configuring & Branding Secure Mobile Apps
Deploying/Publishing Secure mobile apps to Public or Private app stores
Releasing Secured Android & iOS Apps built on Appdome.

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

Features Similar to Block App Overlay Attacks

Here are a few related resources:

How to Prevent abuse of Android Accessibility Service for compromising Android apps
How to Prevent non-approved Android, iOS app store publishing
Check out the Appdome Mobile Fraud Prevention solution page or request a demo at any time.

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.

How to Protect Android Apps from Overlay Attacks & Malware

What are Overlay Attacks ?

Why Block Overlay Attacks in Android Apps?

Blocking Overlay Attacks on Android apps by Using Appdome

Upload the Mobile App to Appdome.

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

Build the feature: Block App Overlay Attacks .

Building Block App Overlay Attacks by using Appdome’s DEV-API:

Building the Block App Overlay Attacks feature via Appdome Console

Certify the Block App Overlay Attacks feature in Android Apps.

Using Threat-Events™ for Overlay Attacks Intelligence and Control in Android Apps

Prerequisites to Using Block App Overlay Attacks :

Thank you!