How to Block Partial Overlays in Android Apps
Learn to Block Partial Overlays in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.
What are Partial Overlay Attacks?
Partial overlay attacks are a type of security threat where malicious software overlays a portion of a user interface on top of legitimate applications on a device. This is typically done without the user’s knowledge or consent. The overlay, which often mimics the look and feel of legitimate UI elements like login screens or payment forms, captures sensitive user inputs such as passwords, credit card details, or other personal information.
The purpose of a partial overlay is to deceive users into interacting with the overlay as if it were part of the legitimate application, thus unknowingly providing their information directly to attackers. This method is less intrusive and might not cover the entire screen, making it harder for users to detect compared to full-screen overlays. It’s a common tactic used in phishing attacks and can be particularly effective on mobile devices where screen real estate is limited, and users might not pay close attention to subtle differences in UI elements.
How Does Blocking Partial Overlays Protect Your Mobile App?
Blocking partial overlays is a crucial security feature for mobile apps, offering several protective measures:
Detection and Prevention: The app detects unauthorized attempts to overlay content and prevents these overlays from executing. This step ensures that only legitimate elements of the app are visible and interactive.
Safeguarding Sensitive Data: By blocking malicious overlays, the app protects sensitive information like login credentials and payment details from being intercepted by attackers.
Integrity of User Interface: Maintaining the integrity of the app’s interface ensures that users interact only with the authentic elements, not deceptive overlays.
Enhancing User Trust: Implementing strong security measures such as overlay protection builds user trust and can help in meeting privacy regulation requirements.
Security Alerts: The app can alert users about potential security threats, increasing awareness and promoting safer usage practices.
These features collectively enhance the security of mobile applications, protecting them from phishing attacks and unauthorized data access.
Prerequisites for Using Block Partial Overlays :
To use Appdome’s mobile app security build system to Block Partial Overlays , you’ll need:
- Appdome account (create a free Appdome account here)
- A license for Block Partial Overlays
- Mobile App (.apk or .aab for Android)
- Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)
Block Partial Overlays on Android apps using Appdome
On Appdome, follow these simple steps to create self-defending Android Apps that Block Partial Overlays without an SDK or gateway:
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Upload the Mobile App to Appdome.
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Upload an app to Appdome’s Mobile App Security Build System
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Upload Method: Appdome Console or DEV-API
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Android Formats: .apk or .aab
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Block Partial Overlays Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
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Build the feature: Block Partial Overlays .
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Building Block Partial Overlays by using Appdome’s DEV-API:
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Create and name the Fusion Set (security template) that will contain the Block Partial Overlays feature as shown below:
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Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Block Partial Overlays feature via Appdome Console, to add the Block Partial Overlays feature to this Fusion Set.
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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 2: Fusion Set Detail Summary
Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory). -
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:
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Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
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Look for sample APIs in Appdome’s GitHub Repository
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Figure 1: Fusion Set that will contain the Block Partial Overlays feature
Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required). -
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Building the Block Partial Overlays feature via Appdome Console
To build the Block Partial Overlays protection by using Appdome Console, follow the instructions below.
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Where: Inside the Appdome Console, go to Build > Anti Fraud Tab > Mobile Fraud Detection section.
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When you enable 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 Partial Overlays
Figure 4: Fusion Set that displays the newly added Block Partial Overlays protection
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Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
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Congratulations! The Block Partial Overlays protection is now added to the mobile app -
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Certify the Block Partial Overlays feature in Android Apps
After building Block Partial Overlays , Appdome generates a Certified Secure™ certificate to guarantee that the Block Partial Overlays protection has been added and is protecting the app. To verify that the Block Partial Overlays 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 Partial Overlays has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Block Partial Overlays and other mobile app security features are in each build of the mobile app
Using Threat-Events™ for Partial Overlays Intelligence and Control in Android Apps
Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when Partial Overlays is detected. To consume and use Threat-Events™ for Partial Overlays in Android Apps, use registerReceiver in the Application OnCreate, and the code samples for Threat-Events™ for Partial Overlays shown below.
The specifications and options for Threat-Events™ for Partial Overlays are:
Threat-Event™ Elements | Block Partial Overlays Method Detail |
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Appdome Feature Name | Block Partial Overlays |
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 | x |
Visible in ThreatScope™ | x |
Developer Parameters for Blocking Partial Overlays Threat-Event™ | |
Threat-Event NAME | |
Threat-Event DATA | reasonData |
Threat-Event CODE | reasonCode |
Threat-Event REF | |
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 |
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 Partial Overlays is detected.
The following is a code sample for native Android apps, which uses all values in the specification above for Block Partial Overlays :
x
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("");
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
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...)
}
};
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
} else {
registerReceiver(threatEventReceiver, intentFilter);
}
x
val intentFilter = IntentFilter()
intentFilter.addAction("")
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
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...)
}
}
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
} else {
registerReceiver(threatEventReceiver, 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(
"",
(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(""));
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...)
}
}
NSNotificationCenter.DefaultCenter.AddObserver(
(NSString)"", // Threat-Event Identifier
delegate (NSNotification notification)
{
var message = notification.UserInfo.ObjectForKey("message"); // Message shown to the user
var reasonData = notification.UserInfo.ObjectForKey("reasonData"); // Threat detection cause
var reasonCode = notification.UserInfo.ObjectForKey("reasonCode"); // Event reason code
var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore"); // Current threat event score
var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore"); // Total threat events score
var variable = notification.UserInfo.ObjectForKey("<Context Keys>"); // Any other event specific context key
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});
window.broadcaster.addEventListener("", 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...)
});
xxxxxxxxxx
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> {
static const String _eventChannelName = ''; // Replace with your EventChannel name
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
String currentThreatEventScore = eventData['currentThreatEventScore']; // Current threat event score
String threatEventsScore = eventData['threatEventsScore']; // Total threat events score
​
// Any other event specific context key
String variable = eventData['<Context Key>'];
});
}
​
// 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 Partial Overlays . 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 Partial Overlays
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 Protect Android Apps from Overlay Attacks & Malware
Block ARM-in-ARM Virtual Devices for Android & iOS Apps
How to Prevent Virtualization to Protect Android Apps
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.