The Security Service, also known as MI5 (Military Intelligence, Section 5), is the United Kingdom’s domestic counter-intelligence and security agency and is part of its intelligence machinery alongside the Secret Intelligence Service (MI6), Government Communications Headquarters (GCHQ) and Defence Intelligence (DI). — Wikipedia

Russia report: MI5 to get more powers

Russia Report: MI5 to Get More Powers -

Boris Johnson is preparing to give the security services more powers to stop foreign interference in Britain after a cross-party report said that the government “took its eye off the ball” over Russia