class SomeController < ApplicationController
  before_filter :protect

  def protect
    allowed = ['127.0.0.1', '123.456.78.9']
    if not allowed.include? request.remote_ip
      # Render a 403 page
      render(:file => File.join(Rails.root, 'public/403'), :status => 403, :layout => false)
      return
    end
  end

  # This won't get executed for those not in the whitelist
  def index
  end
end