VoIP Security Best Practices Every Business Should Know
The VoIP Threat Landscape
VoIP fraud costs businesses billions of dollars annually. The most common attacks include toll fraud (hackers using your phone system to make expensive international calls), eavesdropping on unencrypted calls, and vishing (voice phishing attacks that impersonate your business to defraud customers). Understanding these threats is the first step to preventing them.
Enable End-to-End Encryption (TLS/SRTP)
Unencrypted VoIP calls are vulnerable to interception on any network between your office and the destination. TLS (Transport Layer Security) encrypts the signaling that controls calls, while SRTP (Secure Real-time Transport Protocol) encrypts the actual voice media. Both should be enabled by default in any modern VoIP deployment.
Many legacy VoIP systems transmit calls in plain text by default. If your provider doesn't offer TLS and SRTP encryption, that is a significant security risk that should be addressed immediately.
Harden Your Network with a SBC
A Session Border Controller (SBC) acts as a security firewall specifically designed for VoIP traffic. It hides your internal SIP infrastructure, validates all incoming SIP requests, prevents unauthorized access attempts, and provides topology hiding to prevent attackers from mapping your network. For any business running significant call volume, an SBC is essential.
Implement Strong Authentication
Use strong, unique credentials for every SIP device and never use default passwords. Implement IP allowlisting so that your SIP trunks only accept connections from known IP addresses. Enable multi-factor authentication on all administrative portals. These basic measures eliminate the vast majority of brute-force attacks.
Monitor for Toll Fraud in Real Time
Toll fraud can rack up thousands of dollars in charges within hours. Configure real-time alerts for unusual call patterns: off-hours international calls, sudden spikes in call volume to specific country codes, or any calls to premium-rate numbers. Automatic call blocking rules triggered by these patterns can stop an attack before significant damage is done.
Keep Firmware and Software Updated
Outdated firmware on IP phones and outdated VoIP software are common attack vectors. Establish a regular patching schedule, enable automatic updates where available, and immediately apply security patches when vulnerabilities are disclosed. Subscribe to your VoIP provider's security advisories.
“The companies that get hit with VoIP fraud are almost always running with default credentials, no IP restrictions, and no monitoring. None of these are hard to fix — they just require prioritization.”
— VoIP Security Researcher
Choose a Provider with SOC 2 Alignment
When evaluating VoIP providers, ask about their security certifications and controls. A SOC 2-aligned provider has undergone rigorous third-party audits of their security, availability, and confidentiality controls. This gives you assurance that your calls and data are handled responsibly — and provides documentation for your own compliance requirements.
Related articles
Ready to see MoosePBX for yourself?
Book a demo and see how it fits into your team's workflow.