Inferring the Deployment of Inbound Source Address Validation Using DNS Resolvers

Abstract

This paper reports on the first Internet-wide active measurement study to enumerate networks not filtering incoming packets based on their source address. Our method identifies closed and open DNS resolvers handling requests from the outside of the network with the source address in the prefix of the tested network. The study gives the most complete picture of the inbound Source Address Validation deployment at network providers: 32,673 IPv4 ASes and 197,641 IPv4 BGP prefixes are vulnerable to spoofing of inbound traffic.