The 911 emergency phone lines are critical to US national security, and their infrastructure is considered one of the 16 most critical systems in the nation, with the government investing resources in it accordingly.
In the modern era, a successful cyber-attack against emergency phone lines could be crippling. For the sake of illustration, Imagine being unable to reach the police in crime-ridden Baltimore (currently suffering from considerable unrest). Alternatively, picture the moment of a terror attack, if the public's call to 911 produces nothing more than the triplicate beeps of a busy line.
Three researchers in Ben-Gurion University recently published a paper describing the vulnerabilities of the system (and others like it worldwide). The researchers informed the Department of Homeland Security (DHS) prior to publication; while the findings were published last Saturday in both the printed and online versions of the Washington Post.
The researchers posited an attack carried out by uploading bots to cellphones, which would then dial the local centers without their owners' knowledge. A bot, or chatbot, is a simulated automated conversation.
In North Carolina, for example, just 6000 phones simulating conversations would be sufficient to completely deny service, and just 200 thousand would suffice for the entire country. Worse, all phones are hardwired so that they are able to access emergency call centers even without proper recognition by a local cellphone service. Hence, in the event of an attack, service providers could not even block infected phones from the network.
According to NENA (the national authority responsible for supervising the call centers) they have been aware of the threat for some time and actually informed the DHS about the threat four years ago. Furthermore, according to NENA, the report actually understates the threat.