How to Prevent Strandhogg Task Hijacking

Learn to Prevent Strandhogg Task Hijacking in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is Strandhogg Task Hijacking?

Strandhogg Task Hijacking is an attack that targets the way an application manages its activities. This attack is possible in apps configured to allow exported activities, which are activities that can be accessed by external components or apps enabling them to launch onto the app as tasks.

A ‘task’ refers to a collection of activities that a user interacts with when trying to complete an action within the app. These activities are arranged in a stack known as the back stack in the order in which each activity is opened.

Consider an online stock trading app displaying multiple shares. Clicking on a share opens another screen, which allows several activities. For instance, clicking ‘Deposit’ opens a deposit window, and so forth. Malicious actors use StrandHogg to gain access to personal and confidential information such as login credentials, phone conversations, SMS messages, and photos.

How Does Appdome Prevent Strandhogg Task Hijacking?

To prevent a scenario in which malicious apps misuse these exported activities to perform various harmful actions, Appdome mitigates the attack by adjusting the app’s task usage so that an attacking app cannot exploit its windows. These enhancements lock the app’s activities, effectively countering both Strandhogg 1.0 and 2.0 attack attempts when the app is in the foreground.

Strandhogg 2.0 exploits the Android multi-tasking system to access recently opened apps. To counteract this, Appdome has developed a defense that explicitly removes the app from the multi-task background app menu, thereby protecting the app from being exploited.

IMPORTANT: To successfully protect against Strandhogg 2.0 in devices running up to and including Android 14 it is necessary to omit the app from the recent apps tab. This step is crucial due to the specific way Strandhogg 2.0 exploits the functionalities of the recent apps tab.

We recognize that removing the app from the recent apps menu, particularly when the user is on the login screen, may cause some apps to exhibit unexpected behavior as a result of the enhanced security. In such cases, developers can add the problematic activities to the ‘trusted activities’ list. Appdome will not enforce stringent security measures on activities in this list, and the end user should not experience any interference with the app’s usability.

Prerequisites for Using Prevent Strandhogg Task Hijacking:

To use Appdome’s mobile app security build system to Prevent Strandhogg Task Hijacking , you’ll need:

• Appdome account (create a free Appdome account here)
• A license for Prevent Strandhogg Task Hijacking
• Mobile App (.apk or .aab for Android)
• Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

Prevent Strandhogg Task Hijacking on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Prevent Strandhogg Task Hijacking 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
   4. Prevent Strandhogg Task Hijacking Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps

2. Build the feature: Prevent Strandhogg Task Hijacking.

   1. Building Prevent Strandhogg Task Hijacking by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Prevent Strandhogg Task Hijacking feature as shown below:
      

      Figure 1: Fusion Set that will contain the Prevent Strandhogg Task Hijacking feature
      Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required).

      2. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Prevent Strandhogg Task Hijacking feature via Appdome Console, to add the Prevent Strandhogg Task Hijacking 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:

         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 Prevent Strandhogg Task Hijacking feature via Appdome Console

      To build the Prevent Strandhogg Task Hijacking protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Anti Fraud Tab > Mobile Malware Prevention section.

         Like all other options in ONEShield™, Prevent Strandhogg Task Hijacking is turned on by default, as shown below:

         Figure 3: Prevent Strandhogg Task Hijacking option
         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.

      2. How: Toggle (turn ON) Prevent Strandhogg Task Hijacking, as shown below.
         If needed, Customize the Threat Notification to be displayed to the mobile end-user in a standard OS dialog notification when Appdome Prevents Strandhogg Task Hijacking.

         Figure 3: Prevent Strandhogg Task Hijacking option
         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.

      3. When you select the Prevent Strandhogg Task Hijacking you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Prevent Strandhogg Task Hijacking

         

         Figure 4: Fusion Set that displays the newly added Prevent Strandhogg Task Hijacking protection

      4. Optional Configuration with Prevent Strandhogg Task Hijacking:

         1. Trust Specified Activities Only

            Specify the class name of the activity to exclude from Overlay detection

      5. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).

   Congratulations!  The Prevent Strandhogg Task Hijacking protection is now added to the mobile app

3. Certify the Prevent Strandhogg Task Hijacking feature in Android Apps.

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