There's a concept I remember reading about here, of the idea that you can't just suddenly refuse to answer dangerous questions. You have to consistently refuse to answer some random sample of totally normal questions, so that "refusing to answer a question" doesn't itself become a source of information.

Unfortunately I can't remember what it's usually called, and haven't been able to turn it up via search ("plausible deniability" is way too broad, and I can't find the right narrowing criteria). What is this concept/process called?