FBI special agent Gary Harter of the Washington field office says al-Qaida operatives are highly trained in what is known as "prolonged static surveillance" methods, ranging from using hidden cameras to posing as tourists or even street-corner panhandlers to case a target for terrorism.

He has advised police around the country to be on the lookout for the following possible indicators of terrorist surveillance:

• Discrete use of still cameras, video-recorders, or note-taking at non-tourist type locations.
• Prolonged static surveillance, using operatives disguised as panhandlers, demonstrators, shoe-shiners, food or flower venders, news agents, or street sweepers not previously seen in the area.
• Unusual or prolonged interest in security or personnel, entry points and access controls, or perimeter barriers such as fences or walls.
• Unusual behavior such as staring or quickly looking away from the personnel or vehicles entering or leaving designated facilities or parking areas.
• Observation of security reaction drills or procedures
• Increase in anonymous telephone or e-mail threats to facilities in conjunction with suspected surveillance incidents, indicating possible surveillance of threat-reaction procedures.
• Foot surveillance involving two or three individuals working together.
• Mobile surveillance using bicycles, scooters, motorcycles, cars, trucks, sport-utility vehicles, boats, or small aircraft.
• Use of multiple sets of clothing, identifications, or the use of sketching materials (paper, pencils, etc).
• Questioning of security or facility personnel.