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:

  1. Upload the Mobile App to Appdome.

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

    2. Upload Method: Appdome Console or DEV-API
    3. Android Formats: .apk or .aab
  2. Build the Protection: 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. fusion set that contains Block App Overlay Attacks

        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).

      3. 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.

      4. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set, as shown in Figure 1 above, and get the Fusion Set ID from the Fusion Set Detail Summary (as shown below): fusion Set Detail Summary image

        Figure 2: Fusion Set Detail Summary
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      5. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, App Center, Jenkins, Travis, Team City, Cirlce CI or other system:
        1. Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
        2. Look for sample APIs in Appdome’s GitHub Repository
    2. Building the 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. Block App Overlay Attacks  option

        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

        Fusion Set applied 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 :
        1. Threat-Events™ OFF > In-App Defense

          If the Threat-Events™ setting is cleared (not selected). Appdome will detect and defend the user and app by enforcing Block Overlay Attacks .

        2. 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.

        3. 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 :
        1. Prevent StrandHogg

          Prevent overlay attacks based on StrandHogg, a critical Android vulnerability.

        2. 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
  3. 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: Block App Overlay Attacks  shown in Certificate secure

    Figure 5: Certified Secure™ certificate

    Each Certified Secure™ certificate provides DevOps and DevSecOps organizations the entire workflow summary, audit trail of each build, and proof of protection that 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 DETECTON Appdome detects the attack or threat and passes the event in a standard format to the app for processing (app chooses how and when to enforce).
ON, IN-APP DEFENSE Uses Appdome Enforce mode for any attack or threat and passes the event in a standard format to the app for processing (gather intel on attacks and threats without losing any protection).
Certified Secure™ Threat Event Check
Visible in ThreatScope™
Developer Parameters for 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
messageMessage displayed for the user on event
externalIDThe external ID of the event which can be listened via Threat Events
osVersionOS version of the current device
deviceModelCurrent device model
deviceManufacturerThe manufacturer of the current device
fusedAppTokenThe task ID of the Appdome fusion of the currently running app
kernelInfoInfo about the kernel: system name, node name, release, version and machine.
carrierPlmnPLMN of the device
deviceIDCurrent device ID
reasonCodeReason code of the occured event
buildDateAppdome fusion date of the current application
devicePlatformOS name of the current device
carrierNameCarrier name of the current device
updatedOSVersionIs the OS version up to date
deviceBrandBrand of the device
deviceBoardBoard of the device
buildUserBuild user
buildHostBuild host
sdkVersionSdk version
timeZoneTime zone
deviceFaceDownIs the device face down
locationLongLocation long
locationLatLocation lat
locationStateLocation state
wifiSsidWifi SSID
wifiSsidPermissionStatusWifi SSID permission status
reasonType of overlay
dataOverlay 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 :

Prerequisites to Using Block App Overlay Attacks :

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

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:

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

Protections Similar to Block App Overlay Attacks

Here are a few related resources:

If you have any questions, please send them our way at support.appdome.com or via the chat window on the Appdome platform.

Thank you!

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