I recall that Viet-Nam era secret writing was blown by an Admiral in his memoirs, causing all future terrorists and secret police to photocopy incoming and outgoing mail. This appears to be publicity we could have done without.
WIRED, July 18, 2011
‘The capability of doing mass tracking is possible.’
Around the world, TruePosition markets something it calls “location intelligence,” or LOCINT, to intelligence and law enforcement agencies. As a homeland security tool, it’s enticing. Imagine an “invisible barrier around sensitive sites like critical infrastructure,” such as oil refineries or power plants, TruePosition’s director of marketing, Brian Varano, tells Danger Room. The barrier contains a list of known phones belonging to people who work there, allowing them to pass freely through the covered radius. “If any phone enters that is not on the authorized list, [authorities] are immediately notified.”