The Office of Intelligence Support (OIS) was established in 1977 during the tenure of Treasury Secretary Blumenthal. It succeeded the Office of National Security (ONS), which was set up in 1961 under Treasury Secretary Douglas Dillon to connect Treasury with the work of the National Security Council. The linkage of the ONS's representation of Treasury with the Intelligence Community began under a Presidential Memorandum in 1971 during the tenure of Treasury Secretary William E. Simon. In 1972, in response to the Murphy Commission Report to the Congress, Treasury became a member of the National Foreign Intelligence Board. Today, Executive Order 12333 lists the Special Assistant to the Secretary (National Security) as a senior intelligence officer for the Intelligence Community.

The Special Assistant and his staff support the Secretary of the Treasury in his roles as chief economic and financial adviser to the President of the United States of America, head of the second largest law enforcement department in the federal government, and the official responsible for the integrity of the country's currency. As the focal point on intelligence matters for the Department and Community agencies, the Special Assistant represents the Treasury Department and maintains continuous liaison with other elements of the Central Intelligence Community.

In the most basic of definition, the OIS is a proxy for The Treasury Department in the Central Intelligence Community. It carries the same authority and clout of the Treasury Department, but has a different name.
The above paragraphs are just a history of the Office.