behind closed doors

suljettujen ovien takana, suljetuin ovi|alt=ovin puhekieltä In private; in one's private life; lacking (normal) public disclosure, in camera.

What you do with your girlfriend behind closed doors is none of my business.

Libyas opening home match in the World Cup qualifiers against Cameroon will be played at a neutral venue and behind closed doors, FIFA said on Friday.'' http://in.reuters.com/article/2012/04/20/soccer-world-libya-idINDEE83J07G20120420