Pretty common. Many work contracts have provisions that do not allow the employee to talk about specifics of any company procedure unless its blatantly illegal. In german there is a standing word for it even: "Verschwiegenheitsklausel".
@p7r true enough. Originally coming from the IT world myself that sounds very familiar. To be honest most of the current security procedures in avation are pretty much common knowledge. And sadly many of those procedures are purely window dressing, but don't tell that those hyperactive politicians who think they have shown everyone how hard they clamp down on terrorism when instead they just make travelling a nuisance.