Configuration Medium Clients connecting with anonymous Diffie-Hellman are susceptible to MITM attacks. For deployments using OpenSSL, Anonymous Diffie-Hellman can be disabled by adding "!ADH" to the supported cipher list string. The HTTPS server should be restarted after such a change. Diffie-Hellman is a key-agreement protocol that is used by clients and servers to mutually derive a session key for the HTTPS session. Anonymous Diffie-Hellman is a version without authentication. Vega detected support for anonymous Diffie-Hellman offered by the server. Diffie-Hellman (OpenSSL) HTTPS (Wikipedia)