How to Protect Android Apps from Overlay Attacks & Malware
This Knowledge Base article describes how to use Appdome’s AI/ML in your CI/CD pipeline to continuously deliver plugins that Block Overlay Attacks in Android apps.
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.
Prerequisites for Using Appdome's Block App Overlay Attacks Plugins:
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)
How to Implement Block Overlay Attacks in Android Apps Using Appdome
On Appdome, follow these 3 simple steps to create self-defending Android Apps that Block Overlay Attacks without an SDK or gateway:
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Designate the Mobile App to be protected.
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Upload an app via the Appdome Mobile Defense platform GUI or via Appdome’s DEV-API or CI/CD Plugins.
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Android Formats: .apk or .aab
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Block App Overlay Attacks is compatible with: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps.
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Select the defense: Block App Overlay Attacks .
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Follow the steps in Sections 2.2-2.2.2 of this article to add the Block App Overlay Attacks feature to your Fusion Set via the Appdome Console.
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When you select the Block App Overlay Attacks you'll notice that the Fusion Set you created in step 2.1 now bears the icon of the protection category that contains Block App Overlay Attacks .
Figure 2: Fusion Set that displays the newly added Block App Overlay Attacks protection
Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory). -
Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set. Copy the Fusion Set ID from the Fusion Set Detail Summary (as shown below):
Figure 3: Fusion Set Detail Summary
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Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, Jenkins, Travis, Team City, Circle CI or other system:
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Refer to the Appdome API Reference Guide for API building instructions.
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Look for sample APIs in Appdome’s GitHub Repository.
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Create and name the Fusion Set (security template) that will contain the Block App Overlay Attacks feature as shown below:.Figure 1: Fusion Set that will contain the Block App Overlay Attacks feature
Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required). -
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Add the Block App Overlay Attacks feature to your security template.
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Navigate to Build > Anti Fraud tab > Mobile Fraud Detection section in the Appdome Console.
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Toggle On > Block App Overlay Attacks .
(a) Choose to monitor this attack vector by checking the Threat Events checkbox associated with Block App Overlay Attacks as shown below.
(b) To receive mobile Threat Monitoring, check the ThreatScope™ box as shown below. For more details, see our knowledge base article on ThreatScope™ Mobile XDR.Figure 4: Selecting Block Overlay Attacks
Note: The Appdome Platform displays the Mobile Operation Systems supported by each defense in real-time. For more details, see our OS Support Policy KB. -
Select the Threat-Event™ in-app mobile Threat Defense and Intelligence policy for Block App Overlay Attacks :
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Threat-Events™ OFF > In-App Defense
If the Threat-Events™ setting is not selected. Appdome will detect and defend the user and app by enforcing Overlay Attacks .
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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™ to Block App Overlay Attacks Block Intelligence and Control in Mobile Apps.
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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 to 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 Block Intelligence and Control in Mobile Apps.
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Configure the User Experience Options for Block App Overlay Attacks :
With Threat-Events™ OFF, Appdome provides several user experience options for mobile brands and developers.- App Compromise Notification: Customize the pop-up or toast Appdome uses to notify the user when a threat is present while using the protected mobile app.
- Short message Option. This is available for mobile devices that allow a banner notification for security events.
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Localized Message Option. Allows Appdome users to support global languages in security notifications.
Figure 5: Default User Experience Options for Appdome’s Overlay Attacks
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Block App Overlay Attacks Threat Code™. Appdome uses AI/ML to generate a unique code each time Block App Overlay Attacks is triggered by an active threat on the mobile device. Use the code in Appdome Threat Resolution Center™ to help end users identify, find and resolve active threats on the personal mobile devices.
- Optional Configuration with Block App Overlay Attacks :
- Trust Specified Activities Only
Specify the class name of the activity to exclude from Overlay detection
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Congratulations! The Block App Overlay Attacks protection is now added to the mobile app -
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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 6: 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 |
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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 | |
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message | Message displayed for the user on event |
failSafeEnforce | Timed enforcement against the identified threat |
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. Only available for Android devices. |
deviceID | Current device ID |
reasonCode | Reason code of the occurred event |
buildDate | Appdome fusion date of the current application |
devicePlatform | OS name of the current device |
carrierName | Carrier name of the current device. Only available for Android. |
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 |
threatCode | The last six characters of the threat code specify the OS, allowing the Threat Resolution Center to address the attack on the affected device. |
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 :
Important! Replace all placeholder instances of <Context Key> with the specific name of your threat event context key across all language examples. This is crucial to ensure your code functions correctly with the intended event data. For example, The <Context Key> could be the message, externalID, OS Version, reason code, etc.
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IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("OverlayDetected");
BroadcastReceiver threatEventReceiver = new BroadcastReceiver() {
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
// Current threat event score
String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore");
// Total threat events score
String threatEventsScore = intent.getStringExtra("threatEventsScore");
// Replace '<Context Key>' with your specific event context key
// String variable = intent.getStringExtra("<Context Key>");
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
};
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
} else {
registerReceiver(threatEventReceiver, intentFilter);
}
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val intentFilter = IntentFilter()
intentFilter.addAction("OverlayDetected")
val threatEventReceiver = 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
// Current threat event score
var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore")
// Total threat events score
var threatEventsScore = intent?.getStringExtra("threatEventsScore")
// Replace '<Context Key>' with your specific event context key
// var variable = intent?.getStringExtra("<Context Key>")
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
}
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
} else {
registerReceiver(threatEventReceiver, intentFilter)
}
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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
// Current threat event score
var currentThreatEventScore = userinfo["currentThreatEventScore"]
// Total threat events score
var threatEventsScore = userinfo["threatEventsScore"]
// Replace '<Context Key>' with your specific event context key
// var variable = userinfo["<Context Key>"]
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
);
}
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RegisterReceiver(new ThreatEventReceiver(), new IntentFilter("OverlayDetected"));
class ThreatEventReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
// Message shown to the user
String message = intent.GetStringExtra("message");
// Threat detection cause
String reasonData = intent.GetStringExtra("reasonData");
// Event reason code
String reasonCode = intent.GetStringExtra("reasonCode");
// Current threat event score
String currentThreatEventScore = intent.GetStringExtra("currentThreatEventScore");
// Total threat events score
String threatEventsScore = intent.GetStringExtra("threatEventsScore");
// Replace '<Context Key>' with your specific event context key
// String variable = intent.GetStringExtra("<Context Key>");
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
}
x
NSNotificationCenter.DefaultCenter.AddObserver(
(NSString)"OverlayDetected", // Threat-Event Identifier
delegate (NSNotification notification)
{
// Message shown to the user
var message = notification.UserInfo.ObjectForKey("message");
// Threat detection cause
var reasonData = notification.UserInfo.ObjectForKey("reasonData");
// Event reason code
var reasonCode = notification.UserInfo.ObjectForKey("reasonCode");
// Current threat event score
var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore");
// Total threat events score
var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore");
// Replace '<Context Key>' with your specific event context key
// var variable = notification.UserInfo.ObjectForKey("<Context Keys>");
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
);
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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
// Current threat event score
var currentThreatEventScore = userInfo.currentThreatEventScore
// Total threat events score
var threatEventsScore = userInfo.threatEventsScore
// Replace '<Context Key>' with your specific event context key
// var variable = userInfo.<Context Keys>
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});
x
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class PlatformChannel extends StatefulWidget {
const PlatformChannel({super.key});
State<PlatformChannel> createState() => _PlatformChannelState();
}
class _PlatformChannelState extends State<PlatformChannel> {
// Replace with your EventChannel name
static const String _eventChannelName = "OverlayDetected";
static const EventChannel _eventChannel = EventChannel(_eventChannelName);
void initState() {
super.initState();
_eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
}
void _onEvent(Object? event) {
setState(() {
// Adapt this section based on your specific event data structure
var eventData = event as Map;
// Example: Accessing 'externalID' field from the event
var externalID = eventData['externalID'];
// Customize the rest of the fields based on your event structure
String message = eventData['message']; // Message shown to the user
String reasonData = eventData['reasonData']; // Threat detection cause
String reasonCode = eventData['reasonCode']; // Event reason code
// Current threat event score
String currentThreatEventScore = eventData['currentThreatEventScore'];
// Total threat events score
String threatEventsScore = eventData['threatEventsScore'];
// Replace '<Context Key>' with your specific event context key
// String variable = eventData['<Context Keys>'];
});
}
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
Using Appdome, there are no development or coding prerequisites to build secured Android 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.
Related Articles:
- 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 Detection solution page or request a demo at any time.
How Do I Learn More?
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.