CISA Releases Cyber Risks to 911: TDoS Fact Sheet

Telephony denial of service attacks (TDoS) present a unique risk to public safety communications stakeholders, including Emergency Communications Centers (ECC), Publics Safety Answering Points (PSAP), and other 911 dispatch centers. TDoS events overload communications network elements with telephone calls—disrupting a jurisdiction’s ability to provide emergency response services. In response, the Cybersecurity and Infrastructure Security Agency (CISA) developed the Cyber Risks to 911: Telephony Denial of Service fact sheet to educate the public safety community on TDoS threats. 

Public safety organizations can leverage this fact sheet to familiarize themselves with TDoS threats and mitigation best practices. Specifically, the fact sheet:

  • Overviews common TDoS attack vectors, including mobile phones, botnets, voice over Internet Protocol services, compromised private branch exchanges, preprogrammed landline phones, and variable security standards,
  • Highlights real-world TDoS incidents and impacts, and
  • Provides best practices to mitigate TDoS vulnerabilities.

CISA developed the fact sheet in coordination with public safety stakeholders and cybersecurity subject matter experts to ensure the best practices support the public safety operations environment. Paired with the Cyber Risks to Next Generation 9-1-1 white paper, this fact sheet can improve ECC/PSAP cybersecurity posture. For more information about these documents or TDoS threats, visit or For questions regarding this product, please reach out to CISA at

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