FBI: Telephony denial-of-service attacks can lead to loss of lives

The Federal Bureau of Investigation (FBI) has warned of the harsh consequences of telephony denial-of-service (TDoS) attacks and has also provided the steps needed to mitigate their impact.

The FBI published this warning on Wednesday as an IC3 public service announcement and as a Private Industry Notification issued to private sector organizations in coordination with DHS-CISA.

Attacks on emergency services can lead to loss of lives

TDoS attacks are manual or automated malicious attempts to render telephone systems unavailable by blocking incoming and outgoing calls, which could have terrible consequences when directed at 911 or similar emergency call center operations.

"The objective is to keep the distraction calls active for as long as possible to overwhelm the victim’s telephone system, which may delay or block legitimate calls for service," the FBI said.

"The resulting increase in time for emergency services to respond may have dire consequences, including loss of life."

Threat actors can coordinate such attacks for a wide range of reasons including hacktivism, financial gain, or harassment.

While hacktivists can abuse them to promote their social or political convictions, malicious actors can and have launched TDoS attacks to extort government and private organizations.

They've also been used in the past to disrupt emergency services from answering emergency calls for legitimate requests for help.

Emergency service agencies also targeted in the past

"The IC3 has become aware of increased coercion tactics used by the subjects, which have created a threat to emergency services across the nation," the FBI said in a public service announcement from January 2013.

"The threats have now escalated into a Telephony Denial of Service (TDoS) attacks against the victims' employers, which some have been emergency service agencies.

"The TDoS attacks have tied up the emergency services' telephone lines, preventing them from receiving and responding to legitimate emergency calls."

A separate confidential alert sent to public safety answering points (PSAPs) and emergency communications centers and personnel in March 2013 said that "[i]t is speculated that government offices/emergency services are being 'targeted' because of the necessity of functional phone lines."

As the FBI further added in yesterday's warning, malicious actors provide TDoS services and tools to attackers with varying levels of experience, which drastically lowers the skill level needed to launch such attacks.

TDoS attacks are also challenging to detect, given that attackers spoof the caller ID on every call (in some cases, choosing to spoof the phone numbers of police departments).

This makes it almost impossible to differentiate between malicious and legitimate calls.

FBI's recommendations

FBI's list of recommendations includes measures to take before TDoS attacks, during them, and information on how to report the attacks to the authorities.

The FBI also shared info on how to prepare for 911 outages:

• Before there is an emergency, contact your local emergency services authorities for information on how to request service in the event of a 911 outage. Find out if text-to-911 is available in your area.
• Have non-emergency contact numbers for fire, rescue, and law enforcement readily available in the event of a 911 outage.
• Sign up for automated notifications from your locality if available to be informed of emergency situations in your area via text, phone call, or email.
• Identify websites and follow social media for emergency responders in your area for awareness of emergency situations.