How to remediate – Comelit Intercom Master Detection

1. Introduction

A reachable Comelit master system was detected on the remote host, indicating a potential point of access for unauthorized network communication. This vulnerability affects intercom systems and could allow an attacker to intercept communications or gain control of the system. A successful exploit could compromise confidentiality, integrity, and availability of the intercom system.

2. Technical Explanation

Nessus was able to initiate a CTPP connection with the remote Comelit network, suggesting that the master system is accessible from outside its intended network segment. This indicates an open communication channel which could be exploited for malicious purposes. There are no known CVEs associated with this specific detection at this time. An attacker could potentially use this access to eavesdrop on intercom calls or manipulate system settings.

• Root cause: The Comelit master system is reachable from the network, indicating a lack of proper network segmentation or firewall rules.
• Exploit mechanism: An attacker could initiate a CTPP connection and attempt to send malicious commands to the master system.
• Scope: Comelit Intercom Master systems are affected.

3. Detection and Assessment

To confirm whether a system is vulnerable, first check network connectivity to the Comelit master system. Then perform a thorough scan using Nessus or similar tools.

• Quick checks: Use `ping` or `telnet 3000` to verify basic network connectivity to the master system on port 3000 (default CTPP port).
• Scanning: Nessus vulnerability scan with plugin ID related to Comelit Intercom Master Detection.
• Logs and evidence: Check firewall logs for connections originating from or destined for the Comelit master system’s IP address and port 3000.

ping 

4. Solution / Remediation Steps

To fix this issue, implement network segmentation to restrict access to the Comelit master system. Ensure only authorized devices can communicate with it.

4.1 Preparation

• Ensure you have a rollback plan to revert the firewall rules if needed. A change window may be required depending on your environment and approval processes.

4.2 Implementation

1. Step 1: Create a firewall rule that blocks all inbound connections to the Comelit master system’s IP address except from trusted sources.
2. Step 2: Create a firewall rule that blocks all outbound connections from the Comelit master system except to necessary services.

4.3 Config or Code Example

Before

# Allow all traffic to Comelit master system
iptables -A INPUT -s 0.0.0.0/0 -d  -j ACCEPT

After

# Allow only trusted sources to access Comelit master system
iptables -A INPUT -s /32 -d  -j ACCEPT
iptables -A INPUT -s 0.0.0.0/0 -d  -j DROP

4.4 Security Practices Relevant to This Vulnerability

Network segmentation is crucial for limiting the impact of potential compromises. Least privilege access ensures only authorized devices can communicate with sensitive systems.

• Practice 1: Network segmentation reduces the attack surface by isolating critical systems.
• Practice 2: Least privilege access minimizes the damage an attacker can cause if they gain unauthorized access.

4.5 Automation (Optional)

# Example Ansible playbook snippet to block traffic except from trusted sources
- name: Block all traffic to Comelit master system except from trusted source
  iptables:
    chain: INPUT
    destination: 
    source: 0.0.0.0/0
    jump: DROP
- name: Allow only trusted source to access Comelit master system
  iptables:
    chain: INPUT
    destination: 
    source: /32
    jump: ACCEPT

5. Verification / Validation

Confirm the fix by verifying that only authorized devices can connect to the Comelit master system. Re-run the Nessus scan to ensure the vulnerability is no longer detected. Perform a basic service smoke test to confirm intercom functionality.

• Post-fix check: Use `ping` from an unauthorized host and verify it fails. Then use `ping` from a trusted host and verify it succeeds.
• Re-test: Re-run the Nessus scan with the Comelit Intercom Master Detection plugin to confirm no vulnerabilities are reported.
• Smoke test: Make an intercom call from one internal extension to another to ensure basic functionality remains intact.
• Monitoring: Monitor firewall logs for any unauthorized connection attempts to the Comelit master system’s IP address and port 3000.

ping  # From untrusted host - should fail

6. Preventive Measures and Monitoring

Update security baselines to include network segmentation rules for all critical systems. Implement CI/CD pipeline checks to enforce these rules during deployment, for example using IaC scanning.

• Baselines: Update your firewall baseline or policy to require network segmentation for all intercom master systems.
• Pipelines: Add infrastructure-as-code (IaC) scans to your CI/CD pipeline to automatically detect and prevent misconfigured firewall rules.
• Asset and patch process: Review the configuration of all intercom systems regularly, at least quarterly, to ensure they remain secure.

7. Risks, Side Effects, and Roll Back

• Roll back: Remove the newly created firewall rules to restore the previous configuration.

8. References and Resources

• Vendor advisory or bulletin: https://www.comelitgroup.com/en/