1 One Leak Will Sink A Ship: WebRTC IP Address Leaks Nasser Mohammed Al-Fannah Information Security Group Royal Holloway, University of London Email:
[email protected] Abstract—The introduction of the WebRTC API to modern browsers and mobile applications with Real-Time Commu- browsers has brought about a new threat to user privacy. nications (RTC) capabilities1. Apparently, identifying one or WebRTC is a set of communications protocols and APIs that provides browsers and mobile applications with Real-Time Com- more of the client IP addresses via a feature of WebRTC was 2 munications (RTC) capabilities over peer-to-peer connections. first reported and demonstrated by Roesler in 2015. In this The WebRTC API causes a range of client IP addresses to paper we refer to the WebRTC-based disclosure of a client IP become available to a visited website via JavaScript, even if a address to a visited website when using a VPN as a WebRTC VPN is in use. This is informally known as a WebRTC Leak, Leak. and is a potentially serious problem for users using VPN services The method due to Roesler can be used to reveal a for anonymity. The IP addresses that could leak include the client public IPv6 address and the private (or local) IP address. number of client IP addresses via JavaScript code executed The disclosure of such IP addresses, despite the use of a VPN on a WebRTC-supporting browser. Private (or internal) IP connection, could reveal the identity of the client as well as address(es) (i.e. addresses only valid in a local subnetwork) enable client tracking across websites.