The Intelligence Bureau is the Indian internal intelligence agency and is reputedly the world`s oldest intelligence agency. The Intelligence Bureau was renamed as the Central Intelligence Bureau in 1947 under the Ministry of Home Affairs. The formation of Intelligence Bureau may be due to Major General Sir Charles MacGregor was appointed Quartermaster General and head of the Intelligence Department for the British Indian Army at Simla in 1885. The main objective in those days was to monitor Russian troop deployments in Afghanistan to obstruct the Russian invasion of British India through the Northwest during the late 19th century.

In 1909, the Indian Political Intelligence Office was founded in England in response to the development of Indian revolutionary activities in England, which was named as the Indian Political Intelligence (IPI) from 1921. This was a state-run observation and monitoring agency. The IPI was executed jointly by the India Office and the Government of India and reported together to the Secretary of the Public and Judicial Department of the India Office, and the Director of Intelligence Bureau (DIB) in India, and also preserved close contact with Scotland Yard and MI5. Recently a Private American Intelligence newsgathering Stratfor has listed the Indian Intelligence Bureau as one of the world`s 5 Best Intelligence agencies.

The primary responsibilities of Intelligence Bureau are to garner intelligence from within India and also carry out counter-intelligence and counter-terrorism tasks. The intelligence bureau employs officials from law enforcement agencies mostly Indian Police Service officers as well as from the Indian Army. Other than domestic intelligence responsibilities, the Intelligence Bureau is particularly responsible to maintain the intelligence collection in border areas. This task was particularly stressed after the 1951 recommendations of the Himmatsinhji Committee, also known as the North and North-East Border Committee that is a task commended to military intelligence organizations before independence in 1947. The Intelligence Bureau also executes other external intelligence responsibilities as of 1951.

The Intelligence Bureau activities are highly confidential and no publications other than the internal ones do reveal their arcane workings. Their largely speculative task includes clearance of license to amateur radio professionals. The Intelligence Bureau also passes on intelligence information between other Indian Intelligence agencies and the police. The Intelligence Bureau grants the basic security clearances to Indian diplomats and judges before they take the national oath. On exceptional occasions, Intelligence Bureau officers interact with the media during acute national crisis. Other than inter checking around 6,000 suspicious letters daily, Intelligence Bureau also has email spying software similar to FBI`s carnivore system.

The Intelligence Bureau is also authorized to carry out wiretapping without a warrant. Moreover, the Intelligence Bureau also has numerous authors who are responsible to write letters to various newspapers and magazines and thus supports the government`s viewpoint. The collection mechanisms of the Intelligence Bureau change depending on the region, but the Intelligence Bureau executes its functions both at the state level and the national level. Employees of the Intelligence Bureau carry out the bulk of the intelligence collection strictly internally and only the higher officers execute coordination and higher-level management of the bureau generally. Intelligence Bureau has so far been divided into three categories - namely general, technical and ministerial. This division has different tasks to perform. However, officers from general cadres always get favoured treatment. This is because general cadre with the technical support does most of the intelligence information gathering. The technical cadre and the ministerial cadre provide this information.

Subsidiary Intelligence Bureau is a subsidiary unit of the Intelligence Bureau at the state level that is headed by officers of the rank of Joint Director or above but smaller Subsidiary Intelligence Bureaus are also sometimes headed by Deputy Directors. The Subsidiary Intelligence Bureaus work through their units at district head quarters headed by Deputy Central Intelligence Officers or DCIOs. The Intelligence Bureau maintains an array of field units and headquarters, which are under the control of Joint or Deputy Directors. It is through these offices and the complicated process of delegation that a very `organic` connection between the state police agencies and the Intelligence Bureau is maintained. Moreover, Intelligence Bureau at the national level operates through several units, to keep a record of issues like terrorism, counter-intelligence, VIP security and threat assessment in India.