It is tasked to confront national security threats ranging from subversion or sedition, foreign influence, spying or espionage, domestic or international terrorism, and political or racial/religious extremism.

[1] Deputy Prime Minister Goh Keng Swee stated that 'an efficient secret police' was necessary to counter dangers such as insurgencies and violent rebellions.

It is led by a director, who holds the rank equivalent to a permanent secretary, and reports directly to the Prime Minister's Office (PMO).

[6] During the Malayan Emergency between 1948 and 1960, the CPM attempted to overthrow the government to win independence for Malaya from the British Empire and to establish a socialist economy.

The Singapore SB worked in cooperation with its British and Malayan counterparts to stop the Communist threat by destroying armed cells and rooting out CPM agents embedded within various civil organisations such as trade unions.

Prime Minister Lee Kuan Yew authorised a double agent operation with Wah playing along with the CIA.

After the broadcast, James D. Bell, U.S. ambassador to Malaysia, and the State Department denied the incident, leading a furious Lee to display the letter from Rusk to correspondents.

[11] The denials were withdrawn with a closed congressional record suggesting that the State Department and the ambassador were both unaware of the case as new officials had failed to consult the files.

Close to 80 targets were identified with plans to bomb a shuttle bus ferrying American military personnel and their families from Sembawang to Yishun MRT station.

Other targets included key military installations like the MINDEF Headquarters at Bukit Gombak,[13] U.S. and Israeli Embassies, British and Australian High Commissions, the Singapore American School, and commercial buildings housing US firms.

The powers of investigation and arrest of the ISD are regulated by several laws, including:[17] The following is a list of former directors of the Internal Security Department.