The Vulcan Ministry of Security was a branch of the Vulcan government.
This organization was a part of the Vulcan Council and was charged the security of Vulcan and its assets. The V'Shar and the V'Kor were both part of the Ministry of Security which was headed by the Minister of Security. (Last Unicorn RPG module: The Way of Kolinahr: The Vulcans)
During the early part of the 22nd century, T'Pol worked for the Security Directorate and was responsible for capturing a number of Vulcan operatives that were surgically altered to masquerade as criminal groups on the planet Agaron. Whilst most of the agents returned willingly, a number of refused and were hunted down by the Ministry of Security. (ENT episode: "The Seventh")
By 2154, the Ministry of Security was investigating Vulcan Science Academy instructor T'Les who was under suspicion for stealing classified documents from the Academy itself. She ultimately decided to resign rather then be fired for the scandal involved in the investigation. (ENT episode: "Home") In the same year, the United Earth Embassy was bombed leading to the Security Directorate to dispatch chief investigator Stel to examine the incident which apparently involved the Syrrannite movement. However, he was later framed and arrested by the Vulcan High Command for being involved in the act. (ENT episode: "The Forge")
In 2387, this body met with Captain Data of the USS Enterprise during the time of the Hobus Crisis which threatened to destroy Romulus. The head of security, M'Kan informed Data that whilst he was welcomed, Ambassador Spock was not due to his ties to the Romulan Star Empire. (TNG comic: "Countdown, Number Two")