A security culture is a set of customs shared by a community whose
members may be targeted by the government, designed to minimize risk.
Having a security culture in place saves everyone the trouble of having
to work out safety measures over and over from scratch, and can help
offset paranoia and panic in stressful situations—hell, it might keep
you out of prison, too. The difference between protocol and culture is
that culture becomes unconscious, instinctive, and thus effortless; once
the safest possible behavior has become habitual for everyone in the
circles in which you travel, you can spend less time and energy
emphasizing the need for it, or suffering the consequences of not having
it, or worrying about how much danger you’re in, as you’ll know you’re
already doing everything you can to be careful. If you’re in the habit
of not giving away anything sensitive about yourself, you can
collaborate with strangers without having to agonize about whether or
not they are informers; if everyone knows what not to talk about over
the telephone, your enemies can tap the line all they want and it won’t
get them anywhere.