My client is a bit paranoid and don't want people to visit the people and groups page. This page you can enter from :
site settings ==> Users and Permissions => People and groups
or : Click on the arrow under your name at a office 365 site. and then click people and groups in the top navigation.
From this page people can see all groups and the permissions of these groups. If they click on more (on the quicklaunch) they can even see all groups (even from other sites).
Is there a way to block users from the people and groups page ?