The public voice network has become the target of many attacks, including Telephony Denial of Service (TDoS), robocalls (automated telephone calls), SWATing (anonymously filing police reports to provoke a police raid) and bomb threats. TDoS is a flood of malicious inbound calls that target public-safety response systems such as 911. The Department of Homeland Security, Science and Technology Directorate (S&T) Distributed Denial of Service Defense (DDoSD) is working to shift the advantage from a DDoS attacker to the network administrator by developing the capability to authenticate callers and detect fraudulent call spoofing.