[header] How to recognize signs of terrorist activities [title] Be alert to covert surveillance. [step] Terrorists gather information about a potential target when planning an attack. Acts such as monitoring or recording a security apparatus should raise a red flag. 
If you notice someone who is not involved with a building using the camera on their phone, a camera, or binoculars, be alert. If you see that someone has been drawing diagrams, blueprints or detailed maps, be suspicious.