How to remediate – I Hear U Detection

1. Introduction

I Hear U Detection identifies a VoIP service listening on a remote host. This is a voice over IP application for Linux used to stream audio between two computers, and its presence may indicate unwanted software running on your network. Successful exploitation could allow an attacker to eavesdrop on sensitive conversations or inject malicious audio streams, impacting confidentiality, integrity, and availability of communications.

2. Technical Explanation

The remote service is the UDP port for IHU (I Hear U). The application listens for incoming audio data without strong authentication or encryption by default. An attacker could connect to this port and potentially intercept or manipulate audio streams if the service is accessible from an untrusted network. There is no known CVE associated with this specific detection, but it represents a potential security risk due to its inherent lack of security features. A simple example would be an attacker connecting to the IHU port on a vulnerable system and listening for any transmitted audio data.

• Root cause: The UDP service listens without authentication or encryption.
• Exploit mechanism: An attacker connects to the open UDP port and intercepts audio streams.
• Scope: Linux systems running the IHU application.

3. Detection and Assessment

You can confirm if a system is vulnerable by checking for the listening service or its associated process. A quick check involves verifying the presence of the IHU port, while a thorough method includes examining the running processes.

• Quick checks: Use netstat -tulnp | grep ihud to see if the IHU port is open and which process is listening on it.
• Scanning: Nessus plugin ID 16783 may identify this service, but results should be verified manually.
• Logs and evidence: Check system logs for any activity related to the IHU application or its associated processes.

netstat -tulnp | grep ihud

4. Solution / Remediation Steps

To fix this issue, ensure that the use of this software is in accordance with your organization’s security policy. If the service is unwanted or not needed, disable it or filter incoming traffic to this port.

4.1 Preparation

• Ensure you have a rollback plan in case of unexpected issues. A simple rollback would be to restart the service.
• Consider change window needs and obtain necessary approvals from relevant teams.

4.2 Implementation

1. Step 1: Stop the IHU service using systemctl stop ihud (if applicable).
2. Step 2: Disable the IHU service to prevent it from starting automatically with systemctl disable ihud (if applicable).
3. Step 3: If you need to allow the service, configure a firewall rule to restrict access to trusted networks only.

4.3 Config or Code Example

Before

# No firewall rule exists, service is accessible from all networks

After

iptables -A INPUT -p udp --dport 5004 -s / -j ACCEPT
iptables -A INPUT -p udp --dport 5004 -j DROP

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue. Least privilege reduces the impact if exploited, while input validation blocks unsafe data and safe defaults minimize attack surface.

• Practice 1: Implement least privilege principles to limit access to sensitive services.
• Practice 2: Regularly review running processes for unwanted or unauthorized software.

4.5 Automation (Optional)

#!/bin/bash
# Check if IHU service is running
if systemctl is-active --quiet ihud; then
  # Stop and disable the service
  systemctl stop ihud
  systemctl disable ihud
  echo "IHU service stopped and disabled."
else
  echo "IHU service not found."
fi

5. Verification / Validation

Confirm the fix by checking if the IHU port is no longer listening or if access is restricted to trusted networks. Re-run the earlier detection method to verify the issue is resolved, and perform a simple smoke test of other system functions.

• Post-fix check: Run netstat -tulnp | grep ihud; there should be no output.
• Re-test: Re-run the quick check from section 3 to confirm that the IHU port is closed.
• Smoke test: Verify other network services are functioning as expected.
• Monitoring: Monitor system logs for any unexpected activity related to audio streaming or UDP traffic on port 5004.

netstat -tulnp | grep ihud

6. Preventive Measures and Monitoring

Update security baselines to include checks for unwanted software, add checks in CI/CD pipelines to prevent the deployment of vulnerable applications, and establish a sensible patch or config review cycle.

• Baselines: Update your system baseline to disallow unauthorized software.
• Pipelines: Add checks in your CI/CD pipeline to scan for known vulnerabilities in deployed packages.
• Asset and patch process: Implement a regular security audit of running processes and configurations.

7. Risks, Side Effects, and Roll Back

Stopping the IHU service may impact any applications or users relying on it. If this occurs, restore the service to its previous state by starting and enabling it.

• Risk or side effect 1: Stopping the service may disrupt audio streaming functionality.
• Roll back: Start and enable the service using systemctl start ihud and systemctl enable ihud.

8. References and Resources

• Vendor advisory or bulletin: http://ihu.sourceforge.net/