What is "security theater"

n. security measures which are intended to, or do, provide a feeling or illusion of improved security, while doing little or nothing to actually improve security.

Security theater is the practice of investing in countermeasures intended to provide the feeling of improved security while doing little or nothing to actually achieve it. Some experts such as Edward Felten have described the airport security repercussions due to the September 11, 2001 attacks using commercial jetliners in the United States, as security theater.