On the Feasibility of Launching the Man-In-The-Middle Attacks on VoIP from Remote Attackers

The man-in-the-middle (MITM) attack has been shown to be one of the most serious threats to the security and trust of existing VoIP protocols and systems. For example, the MITM who is in the VoIP signaling and/or media path can easily wiretap, divert and even hijack selected VoIP calls by tempering with the VoIP signaling and/or media traffic. Since all previously identified MITM attacks on VoIP require the adversary initially in the VoIP signaling and/or media path, there is a common belief that it is infeasible for a remote attacker, who is not initially in the VoIP path, to launch any MITM attack on VoIP. This makes people think that securing all the nodes along the normal path of VoIP traffic is sufficient to prevent MITM attacks on VoIP. In this paper, we demonstrate that a remote attacker who is not initially in the path of VoIP traffic can indeed launch all kinds of MITM attacks on VoIP by exploiting DNS and VoIP implementation vulnerabilities. Our case study of Von-age VoIP, the No.1 residential VoIP service in the U.S. mar-ket, shows that a remote attacker from anywhere on the In-ternet can stealthily become a remote MITM through DNS spoofing attack on a Vonage phone, as long as the remote attacker knows the phone number and the IP address of the Vonage phone. We further show that the remote attacker can effectively wiretap and hijack targeted Vonage VoIP calls after becoming the remote MITM. Our results demonstrate that (1) the MITM attack on VoIP is much more realis-tic than previously thought; (2) securing all nodes along the path of VoIP traffic is not adequate to prevent MITM attack on VoIP; (3) vulnerabilities of non-VoIP-specific protocols (e.g., DNS) can indeed lead to compromise of VoIP