Since the 11 September 2001 attacks and naming of the airport as a terrorism target by the Jemaah Islamiyah, the airport's security has been stepped up. Roving patrol teams consisting of SAF and SPF officers, armed with assault rifles or sub-machine guns, patrol the terminals at random intervals.Officers from the Gurkha Contingent are also deployed to patrol the transit areas of the terminal buildings. These measures come at a cost partly borne by travellers in the form of a "passenger security service charge," imposed since 2002.
In 2005 an upgrade in screening technology and rising security concerns led to luggage-screening processes being conducted behind closed-doors, as opposed to them being done just before check-in previously within public view. Carry-on luggage and persons screening are conducted at the individual departure gates, while check-in luggage are screened in the backrooms and secured before loading. A perimeter intrusion detection system for Changi Airport's perimeter fence has also been put in place to further strengthen security of the airfield. while a biometric access control system for staff movement has been put in place since 2006.