TDoS prevention for enterprises

Telephony Denial of Service (TDoS) attacks can overwhelm critical telephone systems, such as emergency response numbers or call centers. The good news: effective solutions are available.


Why would bad actors attack an organization?

  • Competitor trying to shut down your voice communications
  • Criminals diverting attention while hacking another system
  • Hackers preventing calls to financial institutions while making fraudulent charges or transactions
  • Robocallers using auto dialers hit a block of numbers in your facility
    • Perpetrator wasn’t trying to take down your system
    • When their script hits your block of numbers, all your phones start ringing, tying up the lines and staff while distracting attention from critical services
TDoS prevention protects your communications

TDoS prevention

The first defense against TDoS is to use the Trusted IP Address feature in your peering SBC to prevent it from attempting to respond to messages from untrusted IP addresses. This can help defend against TDoS attacks that send packets to your SBC from outside of your established network connections.

With any of these robocall scenarios, attacks can be further mitigated by analyzing call traffic. When the volume of traffic breaches a threshold, further calls are blocked or diverted, ending the attack.

Check the calling numbers for warning signs:

  • On-net calls from external sources (e.g., neighbor spoofing)
  • Invalid
  • Do-not-originate
  • High-risk
  • Poor reputation

Verify the caller ID with STIR/SHAKEN.


Once an inbound call is identified as a potential TDoS attack, you have the following options to mitigate the threat:

  1. Report only, with alerts
  2. Block the call
  3. Send the call to voicemail
  4. Divert the call to a CAPTCHA gateway, which prompts the caller to enter random two digits—humans can do that, but auto dialers cannot and are blocked
  5. Modify the caller display name (CNAM), e.g., <SPAM>, so the called staff member knows when a suspicious call rings

Solution benefits

  • Ensure business continuity in critical telecommunications
  • Enhance corporate resiliency to withstand attacks on communications infrastructure
  • Improve staff efficiency by removing distractions
  • Protect personal information from fraudsters

Our ClearIP and NexOSS software products provide all these capabilities and benefits. Contact us today to learn how TransNexus software can prevent TDoS attacks to enable your staff to continue to deliver excellent service.

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