How to put each user profile private ???

Hello

Thanks for this forum, great ...

I'm french, sorry for english...

Is there a way to put each user profile "private"
I'll try to explain

UserA have her profile, but if userB click on userA link, userB is able to see userA profile.
I would like to know if it's possible to block that ? userA cannot see userB profile or userB cannot see userA profile ...

Thanks for help.