VoIP – Cybersecurity, Risks and Best Practices in 2025
Voice over IP (VoIP) has been at the center of all interactions since its emergence in the world of contact centers. VoIP transmits data from one point to another using packet switching. In short, the human voice is divided into smaller fragments to travel faster through the cloud to the end caller. Once there, the fragments are reassembled and successfully transmit voice data.
VoIP offers countless benefits to businesses in terms of fast communication, better customer service resolution rates, and increased productivity. The big question on everyone’s mind in 2021 is related to cybersecurity attacks, which are impacting contact centers worldwide due to the intensive use of VoIP telephony. Cyberattacks in France quadrupled last year, forcing authorities to strengthen the end-to-end cyber defense chain. Around 70% of business decision-makers are now more than concerned about the high cybersecurity risk their companies face. Who are these attacks targeting? How much damage are they causing? What measures can be taken to stay “safe” from these attacks?
Let’s dive into the world of cybersecurity and see how it can impact your contact center. Today’s businesses are focused on quickly adopting the latest trends, and many business owners have neglected the simple aspect of VoIP security when it comes to data breaches to the point of no return. Large companies like Target, which saw their reputation plummet by approximately 54% a year after their infamous 2013 data breach, are struggling to recover. So, while some large retailers and well-known brands can recover from a data breach, your company likely won’t be so lucky.
1. VoIP Security and Encryption
VoIP phones are more secure than regular landline phones for the simple reason that they have analytics and monitoring capabilities, unlike regular landline phones, which are more expensive to maintain and implement. Encrypted conversations contain unreadable keypads broken down into voice samples that are transmitted from one point to another, preventing them from being deciphered by hackers. Even if intercepted, encryption ensures that hackers will not be able to decipher messages within conversations. For secure transfer, SRPT (Secure Real Time Transport Protocol) is used. It contains AES (Advanced Encryption Standard) for data samples while ensuring message authentication and provides additional security against possible replay. In addition to SRPT, VoIP solutions must be encrypted with Transport Layer Security to protect data such as phone numbers, caller names, and other details. It also prevents tampering with messages and listening to calls. Both TLS and AES are required if you want end-to-end encryption. Servers, internet service providers, hackers, and telecommunications service providers won’t be able to access your communications as long as they’re end-to-end encrypted.
➡️ Here are some comments on security risks and measures to be implemented in order to stop the damage caused by cyber attacks.
a) Sample detection and black hole attacks
Sample sniffing is one of the most common attacks faced by small and medium-sized contact centers. It allows hackers to access unencrypted information contained in voice data packets as they travel from one point to another.
Packet loss occurs when voice data doesn’t reach its destination. Sample sniffers seek to steal information through a packet dropping attack (also known as a black hole attack). Samples are intentionally inserted into your data streams and bypass your router, resulting in a slow connection or data loss.
connection. Using a VoIP VPN helps make your internet lines more secure. End-to-end encryption is also another way to secure your VoIP lines. Setting them up may take some time, but they provide protection against suspicious connections, unrecognized devices, and more through constant network monitoring.
b) DDoS attacks
DDoS (Distributed Denial of Service) attacks, on the other hand, occur when servers are intentionally overwhelmed, preventing businesses from using their own VoIP. The use of botnets (remotely manipulated and controlled robots created by hackers) is the main cause of DDoS attacks. The modus operandi is very simple: Flood all communication channels (websites, servers, and networks) with so much data and requests that they can’t handle them, causing a kind of overload that renders VoIP inoperable.
Common signs are:
- Unexpected and prolonged bandwidth spikes
- 503 HTTP Error Responses
- Slow service
- Unusual traffic from similar devices, IP addresses, and sources.
To mitigate DDoS attacks, VLANs (Virtual Local Area Networks) specifically designed for VoIP traffic are considered the best option to use here, as they make it easier to identify unwarranted and unusual data flows. For users traversing a Wide Area Network (WAN), monitored encryption is the best way to protect your business from DDoS attacks.
c) Vishing
Vishing is similar to phishing. The only difference here is that hackers will use voice communication methods to trick the end user into revealing sensitive information such as passwords, credit card information, security codes, and more. Hackers use a method called “Caller ID spoofing,” which involves making your caller IDs appear legitimate. This could be a call from your local bank stating that your account has been compromised and they need your password to secure it.
Thorough verification methods should be implemented to verify caller identity and phone requests, even if they appear to be coming from an IT department. Another tactic that can be used here is proper agent training. Agents should be instructed not to disclose confidential information unless it has been approved by a supervisor.
The signs of Vishing are:
- Short and unusual numbers appearing on the caller ID display.
- Surprising calls from well-known or famous companies
- Persistent request to provide confidential information for verification purposes.
- A false sense of urgency created by the caller.
How to prevent Vishing:
- Do not provide confidential information over the phone to anyone you suspect.
- Sign up for a Do Not Call Registry
- Do not respond to voicemail messages on the answering machine or by phone.
d) Phreaking attacks
Hackers can access your VOIP network to change calling plans, make international calls, and even add extra calling credits—all through your own system and bank account. They steal stored billing information, access your voicemail, and configure call routing and forwarding policies as they see fit.
How it works: Hackers log into your phone system and then enter a PIN to access an outside line while making calls and charging you for them.
If you notice an increase in your phone bills, unknown numbers in your call history, or calls made outside of business hours, you are likely a victim of phreaking.
Encrypt your SIP, change your passwords regularly, buy ransomware, and most importantly, don’t store billing information in your system.
e) Toll fraud
Hackers are making excessive amounts of international calls from your business phone and taking a portion of the revenue generated by these calls.
International Premium Rate Number (IPRN) providers buy and sell phone numbers from national carriers or regulators. Hackers generate a large number of numbers from these lists and then steal the revenue. Preventing toll fraud is quite simple. Simply enable two-way authentication, restrict location permissions by allowing users to contact a limited number of countries, and finally, set call duration limits.
2. How do you know if your VoIP is secure?
Hackers are making excessive amounts of international calls from your business phone and taking a portion of the revenue generated by these calls.
a) Availability and continuity of service
- What is the guaranteed availability rate (SLA)?
Look for a commitment of at least 99.99%. Also ask what measures are in place to minimize interruptions (network redundancy, automatic failover, etc.). - What are the average resolution times in the event of an incident? A good provider should be able to provide you with a clear history of their average response and recovery times.
b) Cybersecurity and compliance
- How does the company handle security breaches? Demand details on response procedures, automatic alerts and recovery time after an incident.
- Is the provider GDPR, HIPAA, PCI DSS or ISO 27001 certified? These standards are important indicators of cybersecurity maturity. Don’t hesitate to request proof or audit reports.
- What mechanisms are in place to secure on-site servers? This includes firewalls, network segmentation, intrusion detection systems (IDS) and continuous monitoring.
c) Risks specific to VoIP
- What measures are taken against targeted attacks: DNS spoofing, phishing, toll fraud, SIP trunk hijacking? The provider must have active and reactive protections against these threats.
d) Integration with third-party services
- If third-party services are used (CRM, helpdesk, etc.), what security policies apply?
Request an overview of current authentication, encryption and data transmission protocols.
e) Encryption and audio quality
- Are communications end-to-end encrypted (SRTP, TLS)? And most importantly, does this encryption impact call quality? A good provider must offer uncompromising security and performance.
f) Customer support and technical assistance
- What are the assistance options? Ask for details on available channels (phone, chat, email), time slots (24/7 or extended hours), and the levels of support included depending on the plan chosen.
3. Some good practices to adopt in 2025 to secure your VoIP
a) Strengthen password policy
Use centralized management with multi-factor authentication (MFA).
Prohibit weak or reused passwords, and force their automatic rotation every 30 to 60 days via an Active Directory policy or a corporate password manager.
b) Never use public Wi-Fi without protection
Encourage the systematic use of VPNs on unsecured connections.
Integrate Mobile Device Management (MDM) solutions to control mobile device connections.
c) Regularly audit your VoIP infrastructure
Schedule IP telephony-specific penetration tests.
Check SIP firewall configurations, trace abnormal calls and monitor access logs.
d) Continuously update your systems
Automate security updates for softphones, PBXs, VoIP router firmware, etc.
Regularly check that all software and hardware components are up to date against known vulnerabilities (CVEs).
e) Train your teams
Raise awareness among your employees about the risks associated with voice phishing and social engineering.
Integrate VoIP scenarios into your annual cybersecurity training.
4. In conclusion
We hope this article has helped you understand how hackers are taking advantage of VOIP networks when risks exist. Speaking of risks, did you know that Europe has defined a new list of AI-related risks? Cybersecurity should be at the top of your to-do list as an IT manager. In contact centers, data is the greatest asset of all, and securing your data is the most important thing you can do. At Nixxis, we know that prevention is better than cure.
Further reading: Secure your VoIP with the right hosting solution. Will you choose the Cloud or On Premise?
