How will a TDoS attack impact your business?

by Rajesh Haridas, 15 February 2023

While ransomware and data security are receiving so much attention, it may be worthwhile to focus on telephonic security.

Some often-overlooked factors that may already be costing you a fortune

In this article, we will examine some of the frequently neglected security concerns associated with telephony.
Telephony Denial of Service (TDoS) attacks are the most prominent and frequently reported on.

Telephony Denial of Service (TDoS) attacks, also known as "voice denial of service" attacks, entail making a high number of calls to a target telephone system in an attempt to overwhelm it and prevent it from receiving genuine calls.

Because healthcare organizations rely on their telephone systems to connect with patients and other healthcare practitioners, TDoS attacks can have a substantial impact on them.

What is TDoS and how does it work?

TDoS is quite similar to Distributed Denial of Service (DDoS), with the exception that your voice circuits are overwhelmed by constant phone calls.
Consider a SIP trunk or PRI that supports a maximum of 100 simultaneous calls.
  • Your clients would be unable to place calls if malicious callers made more than 100 simultaneous calls over an extended period of time
  • If this is a hospital emergency number for a 911 call center, the results could be fatal
  • This is precisely what an Arizona teen did. He distributed malware that infected the device, resulting in a TDoS attack that took down multiple 911 call centers in Arizona, Washington, and California.

What's the impact of a TDoS attack on you?

TDOS assaults are typically carried out by hacktivists or malicious players seeking financial benefit.
In either case, your business can incur substantial financial and reputational losses.
In recent months, there has been an uptick in TDoS attacks against 911 call centers throughout numerous states in North America.

Recently, a number of hospitals have fallen prey to TDoS attacks.

The TDoS was directed against the hospital's emergency line, preventing actual patients from reaching support. In some instances, the evil players demand ransom.

Due to the convenience of making a SIP call from any endpoint, the majority of TDoS assaults are now automated.
This makes it easier for malicious actors to plan an attack involving hundreds or thousands of hacked devices spread throughout the globe.
VOIP technology has made placing calls from anywhere simpler, cheaper, and untraceable.

In the next article we will go over some of the steps we can take to mitigate TDoS attack.


In today's world, the security of our digital systems is of utmost importance, and while much attention is given to ransomware and data breaches, telephonic security can often be overlooked.

However, Telephony Denial of Service (TDoS) attacks are becoming increasingly common, and businesses must take proactive steps to protect themselves. The consequences of a TDoS attack on healthcare organizations can be particularly devastating.

Malicious actors can overwhelm a phone system with automated calls, causing legitimate callers to be unable to connect. This can have serious, even fatal consequences if it is a hospital emergency line or 911 call center.

By being aware of the risks and taking necessary precautions, businesses can safeguard their telephonic systems and avoid the substantial financial and reputational losses that TDoS attacks can bring.

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