The V'Shar (also referred to as the Vulcan Ministry of Security or the Vulcan Security Directorate) was the Vulcan intelligence agency. After the founding of the United Federation of Planets, the V'Shar often participated in joint operations with Starfleet Intelligence, the Federation Intelligence Service and other such organizations. Even so, they maintained their operational rivalry with the Andorian Am Tal. (TNG: "Gambit, Part II", ENT: "The Forge", Last Unicorn Games, et. al)
During the 2150s, the V'Shar was active in dealing with the Romulan threat to the Coalition of Planets, and thus kept a close watch on their opposite number, the Romulan Tal Shiar. At that time, the V'Shar were aware of the genetic link between Vulcans and Romulans, but kept the fact a highly-classified secret known to only a select few outside the agency. (ENT novel: Kobayashi Maru)
In the 24th century, T'Lena was an operative of the V'Shar for many years before she joined Starfleet Intelligence. She maintained many contacts in the agency, and through them, had access to sources of intelligence well outside Starfleet's sphere of knowledge. (Star Trek: Pendragon).