How to Protect Android Apps Against Apktool Using AI

Last updated November 20, 2023 by Appdome

This Knowledge Base article describes how to use Appdome’s AI in your CI/CD pipeline to continuously deliver plugins that Block Apktool in Android apps.

What Is Apktool?

Apktool is an open-source utility for reverse-engineering Android applications, enabling users to decode APK files, extract resources, and access nearly original source code and assets. While beneficial for legitimate uses like bug fixes, attackers exploit Apktool to analyze, alter, and recompile apps. These attacks can embed malicious code, compromise user data, or manipulate in-app transactions. Apktool-based attacks pose significant risks, such as unauthorized data extraction, app tampering, and republishing altered apps with malware. Defending against these attacks is crucial for safeguarding sensitive app content, ensuring compliance with standards like GDPR and PCI-DSS, and protecting the integrity of app functionality and user data.

How Appdome Protects Mobile Apps Against Apktool?

Appdome’s dynamic Anti-APK Tool plugin for Android protects apps from reverse-engineering attempts using tools like Apktool. The plugin secures app code, resources, and assets against decoding, repackaging, and tampering by monitoring for attempts to extract or modify APK files. Even if extracted, the app remains protected, preventing attackers from embedding malicious code or altering functionality. This protection ensures data integrity, blocks unauthorized modifications, and enhances app security without manual developer effort.

Prerequisites for Using Appdome's Anti-Apktool Plugins:

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

Appdome account (create a free Appdome account here)
A license for Anti-Apktool
Mobile App (.apk or .aab for Android)
Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

How to Implement Block Apktool in Android Apps Using Appdome

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

Designate the Mobile App to be protected.
1. Upload an app via the Appdome Mobile Defense platform GUI or via Appdome’s DEV-API or CI/CD Plugins.
2. Android Formats: .apk or .aab
3. Anti-Apktool is compatible with: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps.
Select the defense: Anti-Apktool.

Create and name the Fusion Set (security template) that will contain the Anti-Apktool feature as shown below:

Figure 1: Fusion Set that will contain the Anti-Apktool feature

Follow the steps in Sections 2.2-2.2.2 of this article to add the Anti-Apktool feature to your Fusion Set via the Appdome Console.

When you enable Anti-Tampering you'll notice that the Fusion Set you created in step 2.1 now bears the icon of the protection category that contains Anti-Apktool.

Figure 2: Fusion Set that displays the newly added Anti-Apktool 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

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:

Refer to the Appdome API Reference Guide for API building instructions.

Look for sample APIs in Appdome’s GitHub Repository.

Add the Anti-Apktool feature to your security template.

Navigate to Build > Security tab > Anti-Reverse Engineering section in the Appdome Console.
Like all other options in ONEShield™, Anti-Apktool is turned on by default, as shown below:
Figure 4: Selecting Anti-Apktool
Note: The App Compromise Notification contains an easy to follow default remediation path for the mobile app end user. You can customize this message as required to achieve brand specific support, workflow or other messaging.

Toggle On Anti-Tampering > Anti-Apktool.

Figure 4: Selecting Block Apktool

Initiate the build command either by clicking Build My App at the bottom of the Build Workflow (shown in Figure 4) or via your CI/CD as described in Section 2.1.4.

Congratulations! The Anti-Apktool protection is now added to the mobile app

Certify the Anti-Apktool feature in Android Apps

After building Anti-Apktool, Appdome generates a Certified Secure™ certificate to guarantee that the Anti-Apktool protection has been added and is protecting the app. To verify that the Anti-Apktool 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 Anti-Apktool has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Anti-Apktool and other mobile app security features are in each build of the mobile app.

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

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

The specifications and options for Threat-Events™ for Apktool are:

Threat-Event™ Elements Block Apktool Method Detail

Appdome Feature Name Anti-Apktool

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 Apktool Threat-Event™

Threat-Event NAME

Threat-Event DATA reasonData

Threat-Event CODE reasonCode

Threat-Event SCORE
currentThreatEventScore Current Threat-Event score

threatEventsScore Total Threat-events score

Threat-Event Context Keys

Timestamp The exact time the threat event was triggered, recorded in milliseconds since epoch

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. Only available for Android devices.

deviceID Current device ID

reasonCode Reason code of the occurred event

deviceBrand Brand of the device

deviceBoard Board of the device

buildUser Build user

buildHost Build host

sdkVersion Sdk version

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.

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 Apktool is detected.

The following is a code sample for native Android apps, which uses all values in the specification above for Anti-Apktool:

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.

IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(""); BroadcastReceiver threatEventReceiver = 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 // Current threat event score String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Total threat events score String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Replace '' with your specific event context key // String variable = intent.getStringExtra(""); // 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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IntentFilter intentFilter = new IntentFilter();
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intentFilter.addAction("");
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BroadcastReceiver threatEventReceiver = new BroadcastReceiver() {
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@Override
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public void onReceive(Context context, Intent intent) {
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String message = intent.getStringExtra("message"); // Message shown to the user
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String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
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String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
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// Current threat event score
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String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore");
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// Total threat events score
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String threatEventsScore = intent.getStringExtra("threatEventsScore");
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// Replace '<Context Key>' with your specific event context key
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// String variable = intent.getStringExtra("<Context Key>");
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// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
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}
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};
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
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registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
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} else {
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registerReceiver(threatEventReceiver, intentFilter);
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}

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 // Current threat event score var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore") // Total threat events score var threatEventsScore = intent?.getStringExtra("threatEventsScore") // Replace '' with your specific event context key // var variable = intent?.getStringExtra("") // 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()
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intentFilter.addAction("")
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val threatEventReceiver = object : BroadcastReceiver() {
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override fun onReceive(context: Context?, intent: Intent?) {
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var message = intent?.getStringExtra("message") // Message shown to the user
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var reasonData = intent?.getStringExtra("reasonData") // Threat detection cause
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var reasonCode = intent?.getStringExtra("reasonCode") // Event reason code
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// Current threat event score
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var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore")
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// Total threat events score
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var threatEventsScore = intent?.getStringExtra("threatEventsScore")
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// Replace '<Context Key>' with your specific event context key
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// var variable = intent?.getStringExtra("<Context Key>")
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// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
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}
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}
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
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registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
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} else {
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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( "", (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 '' with your specific event context key // var variable = userinfo[""] // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...) ); }

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

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 // Current threat event score String currentThreatEventScore = intent.GetStringExtra("currentThreatEventScore"); // Total threat events score String threatEventsScore = intent.GetStringExtra("threatEventsScore"); // Replace '' with your specific event context key // String variable = intent.GetStringExtra(""); // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...) } }

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

NSNotificationCenter.DefaultCenter.AddObserver( (NSString)"", // 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 '' with your specific event context key // var variable = notification.UserInfo.ObjectForKey(""); // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...) } );

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NSNotificationCenter.DefaultCenter.AddObserver(
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(NSString)"", // Threat-Event Identifier
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delegate (NSNotification notification)
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{
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// Message shown to the user
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var message = notification.UserInfo.ObjectForKey("message");
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// Threat detection cause
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var reasonData = notification.UserInfo.ObjectForKey("reasonData");
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// Event reason code
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var reasonCode = notification.UserInfo.ObjectForKey("reasonCode");
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// Current threat event score
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var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore");
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// Total threat events score
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var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore");
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// Replace '<Context Key>' with your specific event context key
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// var variable = notification.UserInfo.ObjectForKey("<Context Keys>");
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// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
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}
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);

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 // Current threat event score var currentThreatEventScore = userInfo.currentThreatEventScore // Total threat events score var threatEventsScore = userInfo.threatEventsScore // Replace '' with your specific event context key // var variable = userInfo. // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...) });

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

import 'dart:async'; import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; class PlatformChannel extends StatefulWidget { const PlatformChannel({super.key}); @override State createState() => _PlatformChannelState(); } class _PlatformChannelState extends State { // Replace with your EventChannel name static const String _eventChannelName = ""; static const EventChannel _eventChannel = EventChannel(_eventChannelName); @override 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 '' with your specific event context key // String variable = eventData['']; }); } // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...) }

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import 'dart:async';
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import 'package:flutter/material.dart';
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import 'package:flutter/services.dart';
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class PlatformChannel extends StatefulWidget {
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const PlatformChannel({super.key});
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@override
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State<PlatformChannel> createState() => _PlatformChannelState();
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}
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class _PlatformChannelState extends State<PlatformChannel> {
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// Replace with your EventChannel name
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static const String _eventChannelName = "";
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static const EventChannel _eventChannel = EventChannel(_eventChannelName);
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@override
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void initState() {
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super.initState();
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_eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
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}
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void _onEvent(Object? event) {
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setState(() {
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// Adapt this section based on your specific event data structure
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var eventData = event as Map;
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// Example: Accessing 'externalID' field from the event
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var externalID = eventData['externalID'];
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// Customize the rest of the fields based on your event structure
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String message = eventData['message']; // Message shown to the user
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String reasonData = eventData['reasonData']; // Threat detection cause
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String reasonCode = eventData['reasonCode']; // Event reason code
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// Current threat event score
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String currentThreatEventScore = eventData['currentThreatEventScore'];
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// Total threat events score
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String threatEventsScore = eventData['threatEventsScore'];
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// Replace '<Context Key>' with your specific event context key
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// String variable = eventData['<Context Keys>'];
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});
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}
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// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
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}

Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Anti-Apktool. 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 Anti-Apktool

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 Build Anti-Debugging in Android & iOS Apps

How to Prevent Android Apps from Running on Emulators

Kotlin Obfuscation

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.

How to Protect Android Apps Against Apktool Using AI

What Is Apktool?

How Appdome Protects Mobile Apps Against Apktool?

Prerequisites for Using Appdome's Anti-Apktool Plugins:

How to Implement Block Apktool in Android Apps Using Appdome

Designate the Mobile App to be protected.

Upload an app via the Appdome Mobile Defense platform GUI or via Appdome’s DEV-API or CI/CD Plugins.

Select the defense: Anti-Apktool.

Add the Anti-Apktool feature to your security template.

Certify the Anti-Apktool feature in Android Apps

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

Related Articles:

How Do I Learn More?

Thank you!

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How Persistent Mobile Identity Delivers Stronger API Protection

How App & Install Binding Stop Social Engineering in Mobile Apps

Eliminating Mobile Ad Fraud with IDAnchor™

Threat-Event™ Elements	Block Apktool Method Detail
Appdome Feature Name	Anti-Apktool
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 Apktool Threat-Event™
Threat-Event NAME
Threat-Event DATA	reasonData
Threat-Event CODE	reasonCode
Threat-Event SCORE
currentThreatEventScore	Current Threat-Event score
threatEventsScore	Total Threat-events score

Threat-Event Context Keys
Timestamp	The exact time the threat event was triggered, recorded in milliseconds since epoch
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. Only available for Android devices.
deviceID	Current device ID
reasonCode	Reason code of the occurred event
deviceBrand	Brand of the device
deviceBoard	Board of the device
buildUser	Build user
buildHost	Build host
sdkVersion	Sdk version
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.