How to Protect iOS Apps from FlyJB Jailbreak Detection Bypass

Last updated November 29, 2023 by Appdome

This Knowledge Base article describes how to use Appdome’s AI/ML in your CI/CD pipeline to continuously deliver plugins that Block FlyJB Jailbreak Detection Bypass in iOS apps.

What is FlyJB?

FlyJB is a jailbreak detection bypass tool that allows users to bypass in-app jailbreak detection mechanisms. It also claims to allow bypassing the built-in DRM (Digital Rights Management) of App Store applications to prevent them from checking whether or not your device is jailbroken. Finally, it claims to disable Substitute or Cydia Substrate, thereby preventing tweaks from hooking into an app.

Jailbreaking is the process of unlocking the iOS operating system on an Apple mobile device. A successful jailbreaking operation is a form of administrative privilege escalation, which bypasses Apple’s restrictions, resulting in full administrative control over the OS (the highest level of administrative privilege possible). Hackers often manage to perform jailbreaking by exploiting bugs in Apple’s software/firmware or modifying system kernels to allow read and write access to the file system.

Why Block FlyJB?

Hackers use Jailbreak Bypass tools like FlyJB to evade Jailbreak detection/protections. Jailbreaking makes it easier to hack iOS apps and to compromise the mobile security model. So if a mobile app is protected with Jailbreak detection or Jailbreak protection, hackers will try to either bypass the protection or hide the fact that the device is Jailbroken and can continue to do whatever activity they used Jailbreak to achieve over a longer period of time and without being noticed.

To avoid detection, hackers combine Jailbreak tools with Jailbreak detection bypass tools to kill two birds with one stone. For example, hackers combine the use of Jailbreak tools such as CheckRa1n,Unc0ver, Zylon, PlankFilza, and Chimera, with Jailbreak Bypass or Jailbreak hiding tools like FlyJB.

Blocking FlyJB in iOS apps is automatically enabled when Block Jailbreak Detection Bypass is enabled in the Fusion Set.

Prerequisites for Using Appdome's Block Jailbreak Bypass Tools Plugins:

To use Appdome’s mobile app security build system to Block FlyJB Jailbreak Detection Bypass , you’ll need:

How to Implement Block FlyJB Jailbreak Detection Bypass in iOS Apps Using Appdome

On Appdome, follow these 3 simple steps to create self-defending iOS Apps that Block FlyJB Jailbreak Detection Bypass without an SDK or gateway:

  1. 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. iOS Formats: .ipa
    3. Block Jailbreak Bypass Tools is compatible with: Obj-C, Java, Swift, Flutter, React Native, Unity, Xamarin, Cordova and other iOS apps.
  2. Select the defense: Block Jailbreak Bypass Tools.

      1. Create and name the Fusion Set (security template) that will contain the Block Jailbreak Bypass Tools feature as shown below:
        fusion set that contains Block Jailbreak Bypass Tools

        Figure 1: Fusion Set that will contain the Block Jailbreak Bypass Tools feature

      2. Follow the steps in Sections 2.2-2.2.2 of this article to add the Block Jailbreak Bypass Tools feature to your Fusion Set via the Appdome Console.

      3. When you select the Block Jailbreak Bypass Tools you'll notice that the Fusion Set you created in step 2.1 now bears the icon of the protection category that contains Block Jailbreak Bypass Tools.

        Fusion Set applied Block Jailbreak Bypass Tools

        Figure 2: Fusion Set that displays the newly added Block Jailbreak Bypass Tools protection
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      4. 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): fusion Set Detail Summary image

        Figure 3: Fusion Set Detail Summary

      5. 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:
        1. Refer to the Appdome API Reference Guide for API building instructions.
        2. Look for sample APIs in Appdome’s GitHub Repository.
    1. Add the Block Jailbreak Bypass Tools feature to your security template.

      1. Navigate to Build > Anti Fraud tab > Mobile Malware Prevention section in the Appdome Console.
      2. Toggle On > Block Jailbreak Bypass Tools.

        (a) Choose to monitor this attack vector by checking the Threat Events checkbox associated with Block Jailbreak Bypass Tools 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.
        Block Jailbreak Bypass Tools option

        Figure 4: Selecting Block FlyJB Jailbreak Detection Bypass

        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.

      3. Select the Threat-Event™ in-app mobile Threat Defense and Intelligence policy for Block Jailbreak Bypass Tools:
        1. 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 FlyJB Jailbreak Detection Bypass .

        2. Threat-Events™ ON > In-App Detection

          When this setting is used, Appdome detects the use of FlyJB 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 Jailbreak Bypass ToolsBlock Intelligence and Control in Mobile Apps.

        3. Threat-Events™ ON > In-App Defense

          When this setting is used, Appdome detects and defends against FlyJB Jailbreak Detection Bypass (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 Jailbreak Bypass ToolsBlock Intelligence and Control in Mobile Apps.

      4. Configure the User Experience Options for Block Jailbreak Bypass Tools:
        With Threat-Events™ OFF, Appdome provides several user experience options for mobile brands and developers.
        1. 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.
        2. Short message Option. This is available for mobile devices that allow a banner notification for security events.
        3. Localized Message Option. Allows Appdome users to support global languages in security notifications.

          Localized Message

          Figure 5: Default User Experience Options for Appdome’s FlyJB Jailbreak Detection Bypass

        4. Block Jailbreak Bypass Tools Threat Code™. Appdome uses AI/ML to generate a unique code each time Block Jailbreak Bypass Tools 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.
    2. 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 Block Jailbreak Bypass Tools protection is now added to the mobile app
  3. Certify the Block Jailbreak Bypass Tools feature in iOS Apps

    After building Block Jailbreak Bypass Tools, Appdome generates a Certified Secure™ certificate to guarantee that the Block Jailbreak Bypass Tools protection has been added and is protecting the app. To verify that the Block Jailbreak Bypass Tools protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below: Block Jailbreak Bypass Tools shown in Certificate secure

    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 Jailbreak Bypass Tools has been added to each iOS app. Certified Secure provides instant and in-line DevSecOps compliance certification that Block Jailbreak Bypass Tools and other mobile app security features are in each build of the mobile app.

Using Threat-Events™ for FlyJB Jailbreak Detection Bypass Intelligence and Control in iOS Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when FlyJB Jailbreak Detection Bypass is detected. To consume and use Threat-Events™ for FlyJB Jailbreak Detection Bypass in iOS Apps, use AddObserverForName in Notification Center, and the code samples for Threat-Events™ for FlyJB Jailbreak Detection Bypass shown below.

The specifications and options for Threat-Events™ for FlyJB Jailbreak Detection Bypass are:

Threat-Event™ Elements Block FlyJB Jailbreak Detection Bypass Method Detail
Appdome Feature Name Block Jailbreak Bypass Tools
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 FlyJB Jailbreak Detection Bypass Threat-Event™
Threat-Event NAME JailbreakBypassDetected
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF 6924
Threat-Event SCORE
currentThreatEventScore Current Threat-Event score
threatEventsScore Total Threat-events score
Threat-Event Context Keys
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.
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
updatedOSVersion Is the OS version up to date
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 Detection cause
data Detection cause data

With Threat-Events™ enabled (turned ON), iOS developers can get detailed attack intelligence and granular defense control in iOS applications and create amazing user experiences for all mobile end users when FlyJB Jailbreak Detection Bypass is detected.


The following is a code sample for native iOS apps, which uses all values in the specification above for Block Jailbreak Bypass Tools:


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.



Using Appdome, there are no development or coding prerequisites to build secured iOS Apps by using Block Jailbreak Bypass Tools. 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 Jailbreak Bypass Tools

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:

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.

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