Yawning, whistling might get you flagged at airport security

A new list says "excessive yawning," "whistling" and "too much laughter" could get you into trouble with airport security agents.

Those gestures, along with "disguises," "face pale from recent shaving of beard," "excessive throat clearing" and "gazing down," all came out in a SPOT (Screening of Passengers by Observation Techniques) referral report. Sources tell ABC News that the report is a "closely held" Transportation Security Administration document which describes the behavior officers look for when observing suspicious travelers and possible terrorists.

"What we know about SPOT suggests it wastes taxpayer money, leads to racial profiling, and should be scrapped," said Hugh Handeyside, staff attorney with the ACLU National Security Project. "The TSA has insisted on keeping documents about SPOT secret, but the agency can't hide the fact that there's no evidence the program works."

The TSA neither confirmed nor denied, according to ABC News, whether indicators listed in the leaked report were actually used by officials. Instead, the agency defended its program overall.

"Behavior detection, which is just one element of the TSA's efforts to mitigate threats against the traveling public, is vital to TSA's layered approach to deter, detect and disrupt individuals who pose a threat to aviation," said a TSA spokesperson. "Looking for suspicious behavior is a common sense approach used by law enforcement and security personnel across the country and the world."

The American Civil Liberties Union recently sued the TSA for not releasing SPOT documents.