Tunneling through DNS over TLS providers

DNS over TLS (DoT) is one of the approaches for private DNS resolution, which has already gained support by open resolvers. Moreover, DoT is used by default in Android operating systems. This study investigates the possibility of creating DNS covert channels using DoT, which is a security threat that benefits from the increased privacy of encrypted communication. We evaluated the performance and usability of DoT tunnels created via commonly used resolvers. Our results show that the performance characteristics of DoT tunnels differ vastly depending on the used DoT resolver; however, the creation of a DoT tunnel is possible, reaching speeds up to 232 Kbps. Moreover, we successfully transferred data via DoT servers claiming Anti-Virus protection and family-friendly content.