The signs are:
â€¢ Elicitation (drawing out information on a setting)
â€¢ Tests of security
â€¢ Acquiring supplies
â€¢ Suspicious people “who don’t belong”
â€¢ Dry runs/trial runs
â€¢ Deploying assets or getting into position.
“I especially like the scenes of concerned citizens calling the police,” Schneier writes. “Anyone care to guess what the false alarm rate would be if everyone started making phone calls like this?”