The rise of Voice over Internet Protocol (VoIP) phone systems has revolutionized business communications.

The ability to make and receive calls over the internet provides unmatched flexibility and cost savings compared to traditional landline systems. However, with all of the benefits VoIP brings, it also introduces new potential security vulnerabilities that businesses need to be aware of.

In this post, we’ll break down the most significant security risks posed by VoIP and what you can do to keep your business communications protected.

The VoIP Environment

Before diving into the specific threats, it’s important to understand what makes the VoIP environment unique. Traditional landline phone systems operate over closed, private networks managed by the telephone company. VoIP, in contrast, sends voice data in digital packets over the public internet. This allows for great features and flexibility but also exposes VoIP systems to security flaws commonly found on the internet.

VoIP systems also integrate voice and data onto a single network. So vulnerabilities that affect your internet traffic can also impact your phone communication. This differs from closed landline networks that keep voice and data separate. Understanding these key differences helps frame the security challenges for VoIP deployments.

Denial of Service Attacks

One of the most common VoIP security risks are denial of service (DoS) attacks. These attacks aim to overwhelm or crash a network by flooding it with fake traffic. DoS attacks are easy to execute and a perennial threat on the internet. VoIP networks are especially vulnerable because of their reliance on open protocols like SIP, RTP, and RTCP for call setup and management.

Attackers can target these protocols directly or leverage botnets to generate massive volumes of junk calls. Either method can tie up all available bandwidth and prevent legitimate calls from going through. DoS attacks can cost businesses thousands in lost revenue and productivity for every minute they are offline.

Eavesdropping and Interception

Another major concern with VoIP is the potential for eavesdropping and call interception. Traditional phones use circuit-switched connections that are difficult to tap into without physical access. VoIP communication travels as data packets that can be intercepted more easily by malicious actors.

Encryption is necessary to prevent snooping on VoIP calls. The most common standard is SRTP, which secures voice packets transmitted between endpoints. However, poor encryption implementation leaves many VoIP systems exposed. Weak ciphers, exchanged keys, and endpoint configuration errors enable call interception and unauthorized wiretapping.

VoIP networks are also susceptible to man-in-the-middle (MITM) attacks. These happen when an attacker inserts themselves into a conversation, secretly relaying messages between both parties. The users believe they are communicating directly, unaware of the third malicious presence listening in. Proper encryption like TLS prevents MITM attacks on VoIP systems.

Malware Infiltration

The integration of voice and data makes VoIP an attractive vector for malware introduction. Malicious code can potentially spread from your data network directly into essential communication systems. VoIP servers run multiple layers of software that cybercriminals can exploit through vulnerabilities.

Successful malware attacks can completely take over VoIP infrastructure. Call recording, call logs, voicemail, auto attendants and more could all become compromised. Malware can also use VoIP systems as a jumping off point to penetrate farther into the corporate network. Keeping VoIP infrastructure patched, secured behind firewalls, and properly configured can help mitigate these risks.

Toll Fraud

Toll fraud, also known as PBX hacking or phreaking, targets weaknesses in VoIP systems to make unauthorized calls. Attackers first scan for vulnerable phone networks, then gain access to place high-volume international calls. The provider ends up bearing the cost of these fraudulent calls that can quickly add up to thousands per minute.

The most common toll fraud method is finding default or common vendor passwords that were never changed. Brute force password attacks and exploiting unpatched vulnerabilities also allow fraudsters access. Proper password policies, lockout mechanisms, OS updates, and scenarios like hidden outbound caller IDs all help defend against toll fraud.

DDoS Against VoIP Infrastructure

Similar to DoS attacks, distributed denial of service (DDoS) poses a threat to VoIP infrastructure availability. DDoS attacks leverage large botnets of compromised devices to overwhelm networks and servers. Floods of traffic can often reach tens of gigabits per second or more – well beyond the capacity of most networks.

The high bandwidth constraints of VoIP communication make it susceptible to DDoS attacks. Even short outages render VoIP systems unusable and unable to place or receive calls. DDoS attacks also frequently target SIP servers and IP phone firmware which can completely halt all voice services. Maintaining VoIP infrastructure redundancy and using DDoS mitigation services helps minimize this threat.

Insufficient Identity Management

Many VoIP security issues arise from insufficient identity management and access control policies. Voice endpoints, VoIP servers, admin interfaces, and more all need proper access restrictions in place. However, organizations often fail to adequately limit access across their VoIP deployments.

Weak credentials, anonymous SIP trunks, unlimited endpoint registrations, and poor partner connection controls enable many of the attacks discussed earlier. A complete identity and access management strategy tailored for VoIP keeps systems properly protected behind policy-based access layers. This reduces the attack surface malicious actors can exploit.

Social Engineering

Social engineering takes advantage of untrained employees and remains one of the top threats to any system. VoIP deployments are no exception. Attackers use techniques like phishing, vishing (voice phishing), and impersonation to manipulate users and gain account or system access.

Ongoing security awareness training is key to preventing social engineering. Educate employees on appropriate call handling, malicious links, suspicious websites, and verifying identities. Multi-factor authentication also helps thwart account takeovers via social tricks.

Insider Threats

While external attacks capture the most attention, insider threats account for a significant portion of security incidents. Rogue employees, poor accountability, and lack of visibility all contribute to insider risk.

VoIP systems face insider issues through intentional and unintentional misuse. Track all administrator access and changes made to VoIP infrastructure. Look out for unauthorized call recordings, hidden call forwards, and tampering with dial plans or routing rules. Make sure you have proper access revocation procedures for employees that leave the organization.

Physical Security Considerations

Don’t overlook physical security when it comes to VoIP protection. SIP servers, gateways, handsets, wiring closets, and network hardware should be physically safeguarded against unauthorized access.

Lock down equipment rooms and use security cameras or access control systems if necessary. Make sure IP phones are under console login for any configuration changes. VoIP deployments require just as much physical layer protection as cybersecurity controls.

Mitigating VoIP Security Risks

After reviewing the range of potential threats, you may wonder if VoIP is too risky compared to traditional telephony. In reality, VoIP brings tremendous value and flexibility that can be secured and protected appropriately. The key is layering the following controls to cover all facets of VoIP security:

  • Firewalls – Firewalls provide fundamental network access control for VoIP systems by restricting traffic. Ensure complete firewall separation between voice/data VLANs.
  • Encryption – Encrypt call media and signaling end-to-end to prevent eavesdropping and interception. Utilize strong protocols including SRTP, TLS, and ZRTP.
  • Access Control – Identity management with tightly restricted access and robust password policies thwarts many attacks. Disable or re-key all default credentials.
  • Vulnerability Management – Actively patch VoIP operating systems, firmware, and applications. Scan regularly for system weaknesses.
  • Monitoring – Look for signs of attacks in progress such as spikes in SIP traffic, SIP errors, and throttled bandwidth. Detect toll fraud through call detail analysis.
  • Resiliency Tools – Implement DoS/DDoS prevention and use tools like TDoS attack mitigation to maintain uptime. Deploy VoIP infrastructure redundantly.
  • Security Training – Educate administrators and users to spot potential VoIP abuse such as robocalling and vishing. Create a security-focused culture.

Applying these controls systematically based on monitoring and vulnerability assessment gives comprehensive protection. As with any security topic, defense in layers maximizes effectiveness while still enabling the benefits of VoIP deployments.

Choosing a Secure VoIP Provider

For organizations utilizing hosted VoIP services, it’s essential to pick a provider that prioritizes security. Avoid vendors that can’t offer details about their specific security practices. Look for the following:

  • Redundant infrastructure with SLA guarantees for reliability
  • Regular third-party penetration testing and audits
  • Endpoint encryption with SRTP and ZRTP support
  • Tier 1 secure data centers with managed firewalls
  • Proactive DDoS mitigation included
  • Dark web monitoring to detect exposed credentials
  • SIP over TLS for secure signaling encryption
  • SOC2 compliance with physical and operational controls

Scrutinizing providers on these criteria minimizes risk while still harnessing the advantages of cloud-hosted VoIP services.

Moving Forward Securely with VoIP

The prominence of VoIP is certain to grow even further in coming years as more businesses transition away from legacy phone systems. With proper planning and security precautions, companies can safely navigate VoIP deployments and address each specific threat.

IP telephony introduces new potential risks, but also empowers organizations through streamlined and unified communication platforms.

Don’t let security fears steer you away from VoIP and causing you to miss out on the tremendous potential benefits.

With methodical security measures and the right provider relationship, VoIP enhances business collaboration and continuity without introducing prohibitive cyber risks.

For a recommended list of leading secure VoIP solutions, see our guide to the best VoIP providers. In it, we break down the best VoIP phone services and cloud platforms based on security, features, reliability, and more.

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