How to protect your VoIP system from a TDoS attack

Posted on Friday January 26, 2024

For all the benefits that Voice over Internet Protocol (VoIP) brings — such as portability, scalability, call quality, and lower costs — it also comes with unique threats. Among these threats is telephony denial-of-service (TDoS). Read on to learn more about TDoS and how to prepare your VoIP systems against it.

What is TDoS?

TDoS is a specific type of denial-of-service (DoS) attack directed at VoIP systems. Unlike typical DoS attacks aimed at IT systems, TDoS is more specialized and is often used against critical services such as hospital phone lines and emergency services. Considering that these phone lines are crucial to saving people's lives, TDoS is a pressing concern. And even more disturbing, some TDoS attackers go as far as demanding ransom, akin to the tactics employed in ransomware attacks.

TDoS attacks are characterized by their efficiency, requiring fewer resources than traditional DoS attacks. In its simplest form, a TDoS attack involves an automated phone dialer repeatedly calling a specific number and disconnecting, preventing others from accessing the line. What makes TDoS a challenge to trace and identify is that attackers use cryptocurrencies and caller-ID spoofing, effectively hiding the identity of the attacker.

What should organizations do to prevent TDoS attacks?

Any business that relies on VoIP for communication must take proactive steps to protect its system against TDoS attacks. VoIP security measures work best when implemented long before an attack happens to effectively ensure your organization is protected from any potential TDoS storm, so make sure to include security measures when your VoIP system is first installed.

However, while fortifying your VoIP system with complex security measures may seem like the best solution, it may hinder business operations. Most businesses rely heavily on seamless communication with customers, partners, and third parties, and stringent security measures can impede this essential function. Instead, you should find a good balance between security and usability.

Here are some strategies to achieve this balance:

Call monitoring: One of the easiest ways to prevent a TDoS attack is by implementing call monitoring to analyze and track call traffic. Once call traffic breaches an established limit, it can be directed to other organizations.

IP address verification: Set up your VoIP to only receive calls from select and verified IP addresses, such as within your service area.

Anti-fraud software: Implement fraud prevention software designed to autonomously analyze multiple phone calls at once for signs indicative of a TDoS attack, such as too many calls from the same origin points or directed at the same destination. Once the software has identified a possible attack in progress, it blocks or reroutes the calls.

Call overflow reserve: Maintain or prepare additional call capacity that can be activated in response to sudden increases in call volume.

Periodic assessment: Perform regular assessments to ensure your VoIP systems have the necessary call capacity (both primary and reserve), no matter the volume of traffic. Use the results of these assessments to identify and correct weaknesses in your VoIP system.

Education: Train your employees to recognize the signs of a TDoS attack and implement the necessary protocols to mitigate it.

Continuity of operations agreements: Organizations that receive calls related to healthcare or demands for emergency services need to establish agreements with similar organizations who can provide service during a TDoS attack.

Protect your VoIP from TDoS and other threats. Connect with one of our IT specialists today.