An account of INS's successful efforts to intercept Sikh terrorists in 1988 illustrates its role as the country's first line of defense against terrorist incursions. The article describes the Intelligence Program, the INS unit that is the focal point for collecting information on terrorists. Also discussed are liaison activities and lookout systems -- manual and automated -maintained at points of entry. Another key area considered is the detection of fraudulent documents through the Forensic Document Library connected to major ports of entry through Photophone and issuance of alerts on encountered counterfeit documents. The article examines training provided by INS for its officers, representatives of foreign governments, and airline personnel. Other INS services detailed include intelligence collection and the Redbook, a handbook identifying spurious documentation used by terrorist groups.