That. I was contractor once, we obviously were allowed to say what we did to various degrees. Like working on picture analysis or analyzing operational data and so on. But not about the actual details. Even the projects and so on were usually only refered to indirectly. After that, it usually just took 5 minutes on Google to find out what it was. Say supporting a new military aircraft program for the German armed forces, that left you with two options. Again, we never talked about the details, say prices, data and so on. And I won't. Nor will I talk about concrete data from my days at Amazon.
But, yeah, I very much talk about what I did. Would be quite difficult to pass interviews and get projects, wouldn't it?
Same goes for the real secret stuff. Saying you worked abroad for the CIA is much different from saying you served as a CIA operative in Afghanistan between 2001 and 2004. Unless, of course, you get an official legend fot your life after.
There's no reason for all of this.
It's perfectly reasonable for people to say 'I work on iOS' or I work on 'new hardware but I can't say much more than that', or 'I work in production for Apple TV'.
Most people at most companies are not allowed to talk about the details of what they do.