Routes: Root as Users#Show

I'd like to define the root path of my site as the Users#Show action,
therefore whenever someone goes to they will see
their own profile page.
At the moment I have done this by having the following in my routes.rb
  # Home Page
  map.root :controller => 'users', :action => 'show'

The Users controller then looks like:
  def show
    @user = current_user

This works with respect to showing each users profile page on the route
page. However, if tries to go to
they still see their profile page because I am setting @user to
current_user no matter what the request.
I need to return 404 pages when users go to:

What is the correct way to do this?

In the controller, couldn't you look for/at params[:id] to see if the
request was for a user other than themselves?