How Eavesdropping is Possible on a FreePBX Server

1. SIP Traffic Interception (Man-in-the-Middle Attack)

If SIP traffic is unencrypted, attackers on the same network can sniff and capture voice calls.

How it happens: Using tools like Wireshark, an attacker can capture RTP packets and reconstruct the conversation.

Prevention:

• Use SIP over TLS (SIPS) to encrypt SIP signaling.
• Enable SRTP (Secure RTP) to encrypt voice traffic.
• Use a VPN to encapsulate VoIP traffic.

2. Weak or Default Credentials

If FreePBX admin interface or SIP accounts use default or weak passwords, attackers can log in and listen to live calls.

How it happens: Attackers brute-force SIP extensions, register as a rogue endpoint, and listen to conversations.

Prevention:

• Set strong passwords for SIP extensions and admin panel.
• Change default admin credentials.
• Use fail2ban to block brute-force attempts.

3. Unauthorized Call Recording

If call recording is enabled and an unauthorized user gains access, they can listen to recorded calls.

How it happens: A compromised admin account or malware accessing stored recordings.

Prevention:

• Restrict call recording permissions.
• Store recordings on an encrypted file system.
• Audit CDR logs for unauthorized access.

4. ARP Spoofing or Network Packet Sniffing

If FreePBX is on a shared network, an attacker can spoof the ARP table and intercept VoIP traffic.

How it happens: Tools like Ettercap and Bettercap allow an attacker to redirect SIP/RTP traffic.

Prevention:

• Use VLANs to isolate VoIP traffic.
• Enable port security on network switches.
• Implement 802.1X authentication.

5. Unauthorized Access to Asterisk CLI

If an attacker gains access to the FreePBX server via SSH, they can listen to live calls using Asterisk commands.

How it happens: Commands like “chanspy” allow call monitoring.

Prevention:

• Disable root SSH access.
• Use firewall rules to restrict SSH access.
• Enable Two-Factor Authentication for FreePBX.

6. WebRTC Vulnerabilities

If FreePBX uses WebRTC, attackers might exploit leaks or vulnerabilities to capture calls.

Prevention:

• Keep FreePBX and WebRTC updated.
• Disable WebRTC if not needed.
• Use a secure STUN/TURN server.

7. SIP Trunk Hacking

If an attacker gains access to SIP trunk credentials, they can route calls through your PBX.

Prevention:

• Lock SIP trunks to a specific IP address.
• Use strong authentication for SIP providers.
• Monitor SIP logs for unusual activity.

8. Social Engineering & Insider Threats

An insider with FreePBX access can enable call recording or spy on calls.

Prevention:

• Limit access privileges using FreePBX roles.
• Regularly audit access logs.
• Log all call recordings and admin access.

Final Security Measures

• Use FreePBX Firewall and iptables to block unauthorized access.
• Enable fail2ban to prevent brute-force attacks.
• Encrypt SIP and RTP traffic using TLS and SRTP.
• Keep FreePBX and Asterisk updated.
• Monitor FreePBX logs for anomalies.

By securing these weak points, you can prevent eavesdropping and keep your FreePBX system safe.