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Constraining Device Trust Bypass Attacks Against NetBird Zero Trust Networks Through Device Identity and Access-Policy Validation

Description

Modern organizations use Zero Trust Network Access (ZTNA) to provide controlled connectivity between users, devices, and internal resources without automatically trusting a device simply because it is connected to an internal network.

A core Zero Trust principle is that access should depend not only on user identity but also on the security state and trustworthiness of the requesting device.

NetBird is an open-source Zero Trust networking platform that provides identity-based networking and secure connectivity between authorized peers.

However, if device identity and access policies are incorrectly configured, an unauthorized or untrusted device may attempt to obtain network access to protected resources.

In this use case, NetBird is deployed as the controlled Zero Trust networking platform on Ubuntu Linux inside an isolated VirtualBox laboratory.

A controlled internal application is deployed as a protected resource. Authorized and unauthorized laboratory devices are created to represent different device-trust states.

A controlled Device Trust Bypass scenario is performed from Kali Linux. The assessment evaluates whether an unauthorized device can obtain or retain network access to a protected resource without satisfying the required Zero Trust device and access policies.

NetBird access policies are used to define which peers are permitted to communicate. NetBird management and peer information is used to establish device identity and connectivity state.

Wazuh is used for security monitoring, while OpenSearch is used for centralized investigation and event correlation.

After identifying the device-trust weakness, peer access policies are strengthened and unauthorized device connectivity is removed. The same controlled device-access scenario is then repeated to verify that untrusted devices cannot access protected resources while authorized devices continue to function normally.

The complete Zero Trust workflow is: Protected Resource → NetBird Zero Trust Network → Authorized Device → Device Identity → Access Policy → Controlled Untrusted Device → Device Trust Bypass Attempt → Access Decision → Security Detection → Policy Remediation → Device Restriction → Retesting → Zero Trust Validation

Existing Security Problem

Application: NetBird Zero Trust Network

NetBird is the real open-source Zero Trust networking platform used in this project.

Existing Problem:

Traditional network access may rely heavily on network location. If a device is connected to an apparently trusted network, it may receive access to internal resources even when its security state has not been adequately validated.

The security problem is therefore:

Untrusted Device → NetBird Network → Insufficient Device Access Policy → Protected Resource → Unauthorized Network Connectivity → Potential Data / Application Access

Attack

Specific Attack: Device Trust Bypass

The controlled attack scenario evaluates whether an unauthorized laboratory device can obtain network connectivity to a protected resource despite not satisfying the intended device-access policy.

Attack Behavior:
Protected Application
→
NetBird Zero Trust Network
→
Authorized Device
→
Device Identity / Access Policy
→
Controlled Untrusted Device
→
Device Trust Bypass Attempt
→
Unauthorized Peer Connectivity
→
Protected Resource Access
→
Security Monitoring
→
Device Access Restriction
→
Policy Remediation
→
Retesting
→
Unauthorized Connectivity Blocked

Security Concept

Device-Centric Zero Trust and Continuous Access Validation:

The primary Zero Trust security concept is Device-Centric Zero Trust.

A user should not automatically receive access simply because the device is connected to the organization's Zero Trust network. Instead, access should be evaluated using: User Identity + Device Identity + Device Trust State + Destination + Access Policy - > Authorization Decision. The objective is to prevent an unauthorized device from obtaining network access to protected resources simply because it can reach the Zero Trust networking infrastructure.

The secure processing flow is:

Access Request
→
Device Identification
→
Identity Verification
→
Policy Evaluation
→
Authorization Decision
→
Protected Resource
→
Continuous Monitoring

Defensive Mechanism

Device Identity

Each authorized laboratory device is assigned a unique NetBird peer identity.

Purpose

Distinguish authorized devices from unauthorized devices.

Peer Authorization

NetBird access policies determine which peers can communicate.

Purpose

Prevent unauthorized device-to-device connectivity.

Least-Privilege Network Access

Devices receive only the network access required for their legitimate function.

Purpose

Reduce unnecessary connectivity.

Protected Resource Segmentation

Sensitive services are placed behind explicit access policies.

Purpose

Prevent unrestricted access from connected peers.

Default-Deny Access Policy

Unapproved device communication is denied.

Purpose

Prevent implicit trust between network peers.

Device Access Revocation

Unauthorized or compromised devices can be removed from the permitted access policy.

Purpose

Prevent continued access by untrusted devices.

Continuous Peer Monitoring

NetBird peer connectivity is monitored.

Purpose

Identify unexpected devices and communication relationships.

Security Event Monitoring

Wazuh monitors relevant Ubuntu and NetBird activity.

Purpose

Detect changes and suspicious access behavior.

Centralized Investigation

OpenSearch is used to correlate device, network, and security events.

Purpose

Establish the timeline of the device-trust violation.

Post-Remediation Validation

The original device-access scenario is repeated after remediation.

Purpose

Confirm that unauthorized devices remain unable to access protected resources.

Security Tools

Target Zero Trust Platform: NetBird

NetBird is the primary Zero Trust networking platform.

Purpose
  • Establish secure peer networking.
  • Provide peer identities.
  • Define network-access policies.
  • Control device-to-device connectivity.
  • Support Zero Trust segmentation.

Network Connectivity Tool: WireGuard

WireGuard provides the secure network tunnel technology used by NetBird.

Purpose
  • Establish encrypted peer communication.
  • Provide secure network connectivity.
  • Support controlled peer-to-peer communication.

Network Validation Tool: Nmap

Nmap is used to validate protected-resource reachability.

Purpose
  • Identify reachable laboratory services.
  • Validate network exposure.
  • Test protected-resource accessibility.
  • Compare access before and after policy remediation.

Security Monitoring Tool: Wazuh

Wazuh is used for centralized security monitoring.

Purpose
  • Monitor Ubuntu activity.
  • Monitor relevant NetBird activity.
  • Detect security events.
  • Monitor configuration changes.
  • Generate security alerts.

Security Investigation Platform: OpenSearch

OpenSearch is used for centralized security investigation.

Purpose
  • Search security events.
  • Correlate device-access activity.
  • Review timestamps.
  • Investigate policy violations.
  • Establish the incident timeline.

Protected Application: Internal Web Application

A controlled web application is deployed as the protected resource.

Purpose
  • Represent a sensitive internal service.
  • Provide a resource protected by Zero Trust policies.
  • Generate legitimate application traffic.
  • Validate authorized and unauthorized device access.

Target Platform: Ubuntu Linux

Ubuntu hosts NetBird and the protected application.

Purpose
  • Run NetBird components.
  • Host the protected resource.
  • Generate system activity.
  • Support security monitoring.

Security Testing Platform: Kali Linux

Kali Linux provides the controlled untrusted-device testing environment.

Purpose
  • Represent an unauthorized device.
  • Perform controlled access tests.
  • Validate NetBird policies.
  • Perform post-remediation testing.

Virtualization Platform: VirtualBox

VirtualBox provides the isolated Zero Trust laboratory.

Purpose
  • Host Ubuntu.
  • Host Kali Linux.
  • Provide isolated networking.
  • Maintain a reproducible Zero Trust environment.

Process

STEP 01

Step 1: Prepare the Isolated Zero Trust Laboratory

  • Install VirtualBox.
  • Create an Ubuntu virtual machine.
  • Create a Kali Linux virtual machine.
  • Configure an isolated virtual network.
  • Assign laboratory IP addresses.
  • Verify connectivity between the virtual machines.
  • Ensure the environment is isolated from production systems.
Tools: VirtualBox + Ubuntu + Kali Linux
STEP 02

Step 2: Deploy NetBird

  • Install NetBird on the laboratory Ubuntu environment.
  • Start the required NetBird components.
  • Verify that the NetBird environment is operational.
  • Configure the laboratory network.
  • Verify that peer information is available.
  • Record the initial configuration.
Tools: NetBird
STEP 03

Step 3: Deploy the Protected Application

  • Deploy a controlled internal web application on Ubuntu.
  • Configure the application as a protected resource.
  • Verify that the application is operational.
  • Record the application's network endpoint.
  • Confirm that the resource is reachable only through the laboratory Zero Trust network.
Tools: Ubuntu + NetBird
STEP 04

Step 4: Establish Authorized Device Connectivity

  • Configure an authorized laboratory device.
  • Register the device with the NetBird environment.
  • Verify that the peer receives its expected identity.
  • Establish authorized connectivity.
  • Confirm access to the protected application.
  • Record the authorized device baseline.
Tools: NetBird
STEP 05

Step 5: Establish the Secure Access Baseline

  • Review the authorized peer configuration.
  • Identify the protected application.
  • Record the expected communication path.
  • Verify authorized access.
  • Verify that unauthorized communication is not permitted.
  • Preserve the baseline for comparison.
Tools: NetBird + Nmap
STEP 06

Step 6: Configure Zero Trust Device Policies

  • Define authorized peer groups.
  • Define protected-resource access requirements.
  • Restrict communication to approved devices.
  • Apply least-privilege access.
  • Configure default-deny behavior for unnecessary connectivity.
  • Verify legitimate access.
Tools: NetBird
STEP 07

Step 7: Configure Secure Peer Communication

  • Verify that NetBird peer communication uses the secure networking mechanism.
  • Review WireGuard connectivity.
  • Verify encrypted peer communication.
  • Record the secure network baseline.
  • Confirm that authorized peers can communicate correctly.
Tools: NetBird + WireGuard
STEP 08

Step 8: Configure Security Monitoring

  • Configure Wazuh to monitor relevant Ubuntu and NetBird activity.
  • Monitor peer and configuration activity.
  • Monitor relevant authentication and system events.
  • Verify that security telemetry is collected.
  • Establish the normal monitoring baseline.
Tools: Wazuh
STEP 09

Step 9: Establish Normal Authorized Access

  • Use the authorized laboratory device.
  • Connect to the protected application.
  • Generate normal application traffic.
  • Review the NetBird connectivity state.
  • Review Wazuh events.
  • Confirm legitimate access remains functional
Tools: NetBird + Wazuh
STEP 10

Step 10: Introduce the Controlled Untrusted Device

  • Within the isolated laboratory:
  • Use Kali Linux as the untrusted laboratory device.
  • Register or represent the device according to the controlled test design.
  • Record its peer identity.
  • Do not use any real organization's device identity.
  • Maintain the simulation entirely within the laboratory.
Tools: Kali Linux + NetBird
STEP 11

Step 11: Perform the Controlled Device Trust Bypass Attempt

  • Using the untrusted laboratory device:
  • Attempt to communicate with the protected application.
  • Attempt to establish the required network connectivity.
  • Observe the NetBird access decision.
  • Record whether communication is permitted.
  • Preserve the test evidence.
Tools: Kali Linux + NetBird
STEP 12

Step 12: Validate Protected-Resource Reachability

  • Use Nmap from the controlled test device.
  • Check the reachability of the protected application.
  • Compare the result with the intended Zero Trust policy.
  • Determine whether the untrusted device can reach the protected service.
  • Record the result.
Tools: Nmap
STEP 13

Step 13: Detect the Device-Trust Violation

  • Review Wazuh events.
  • Identify the untrusted device activity.
  • Review available peer information.
  • Review timestamps.
  • Identify policy or connectivity changes.
  • Determine whether the activity represents a device-trust violation.
  • Preserve the detection evidence.
Tools: Wazuh
STEP 14

Step 14: Investigate the Security Event

  • Open relevant Wazuh events in OpenSearch.
  • Review the device identity.
  • Review the protected destination.
  • Review connectivity events.
  • Correlate timestamps.
  • Establish the sequence of the access attempt.
  • Document the incident timeline.
Tools: Wazuh + OpenSearch
STEP 15

Step 15: Assess the Zero Trust Risk

  • Evaluate:
  • Device identity.
  • Peer authorization.
  • Protected-resource sensitivity.
  • Network access policy.
  • Unauthorized connectivity.
  • Security monitoring visibility.
  • Potential data exposure.
  • Potential application impact.
  • Policy effectiveness.
  • Remediation requirements.
  • Assign an appropriate security risk level.
Tools: NetBird + Nmap + Wazuh + OpenSearch
STEP 16

Step 16: Remediate the Device Trust Weakness

  • Remove unauthorized peer access.
  • Strengthen device-access policies.
  • Apply default-deny communication.
  • Restrict protected-resource access to authorized devices.
  • Revoke unnecessary peer permissions.
  • Verify the corrected Zero Trust configuration.
  • Confirm the unauthorized peer is no longer permitted.
Tools: NetBird
STEP 17

Step 17: Retest Unauthorized and Authorized Device Access

  • Unauthorized Device Retest
  • Use the same controlled Kali Linux device.
  • Attempt to reach the protected application again.
  • Verify that connectivity is denied.
  • Use Nmap to confirm the protected service is no longer reachable.
  • Record the result.
  • Authorized Device Retest
  • Use the legitimate laboratory device.
  • Access the protected application.
  • Verify that authorized connectivity succeeds.
  • Confirm that legitimate application functionality remains operational.
Tools: Kali Linux + NetBird + Nmap
STEP 18

Step 18: Perform Final Zero Trust Security Validation

  • Review the original device-trust bypass evidence.
  • Review NetBird peer identities.
  • Review NetBird access policies.
  • Review WireGuard connectivity.
  • Review Nmap reachability results.
  • Review Wazuh security events.
  • Review OpenSearch investigation results.
  • Compare the original and remediated access behavior.
  • Confirm unauthorized devices cannot reach the protected resource.
  • Confirm authorized devices continue to function normally.
  • Document the final Zero Trust Security assessment.
Tools: NetBird + WireGuard + Nmap + Wazuh + OpenSearch + Kali Linux

Outcome

  1. A real NetBird Zero Trust networking environment is successfully deployed on Ubuntu, providing a practical open-source platform for demonstrating device-centric Zero Trust security.
  2. Authorized laboratory devices are assigned distinct peer identities, establishing identity-aware network access.
  3. A protected internal web application is successfully placed behind Zero Trust access policies, creating a controlled protected-resource environment.
  4. A controlled Device Trust Bypass scenario is successfully reproduced, demonstrating the risk of allowing an unauthorized device to obtain access to protected resources.
  5. NetBird access policies enforce device-based network authorization, restricting communication according to explicitly permitted peer relationships.
  6. WireGuard provides secure peer communication, ensuring that authorized network connectivity uses encrypted tunnels.
  7. Nmap validates protected-resource reachability, providing direct evidence of whether unauthorized devices can access the protected service.
  8. Wazuh and OpenSearch provide centralized monitoring and investigation, allowing device-access activity and policy violations to be identified and analyzed.
  9. Unauthorized peer access is removed and Zero Trust device-access policies are strengthened, and post-remediation testing confirms that unauthorized devices cannot reach the protected resource while authorized devices continue to operate.
  10. The complete Zero Trust device identity, device trust, peer authorization, micro-segmentation, Device Trust Bypass assessment, security monitoring, investigation, access-policy remediation, and post-remediation validation workflow is successfully demonstrated.
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