What is the intelligence service of UK?

Answer 1

The UK has several Intelligence Services: *The Security Service, better known as MI5, which is responsible for security intelligence. Operates both domestically and overseas.
Reports to Home Office.
Equivalent to ASIO, CSIS, FSB, and FBI National Security Division.
*Secret Intelligence Service (SIS), better known as MI6, which is responsible for collecting foreign intelligence. Operates both domestically and abroad.
Equivalent to ASIS, CIA, SVR, and CSIS.
Reports to Foreign Office.
*Government Communications Headquarters, or GCHQ for short. Primarily responsible for SIGINT (signals intelligence) and data storage.
Equivalent to DSD, NSA, etc.
Reports to Foreign Office.
*Joint Intelligence Committee, or JIC, is responsible for high-level coordination of the UK's Intelligence Services. Part of the Cabinet Office.
*Defence Intelligence Staff, or DIS, performs high-level analysis from different Intelligence Services and is a part of Ministry of Defence.
Equivalent to DIO.
*JARIC - The National Imagery Exploitation Centre, is responsible for GEOINT and employs spy satellites. Reports to Ministry of Defence.
Equivalent to DIGO.
*Special Branch, whilst not an intelligence service as such, plays a vital role in Britain's national security. Responsible for aiding the Security Service in the art of taking out terrorists. Also responsible for making arrests during intelligence investigations, as the Security Service has no police powers of arrest (although the Service sometimes kidnaps people when necessary). Also responsible for providing personal security for non-Royal VIPs.
Reports to the Home Office.