diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -69,6 +69,7 @@
       if (not user.admin? and user.last_ip and user.last_ip != request.remote_ip)
         flash[:notice] = "You cannot use the system from #{request.remote_ip}. Your last ip is #{user.last_ip}"
         redirect_to :controller => 'main', :action => 'login'
+        puts "CHEAT: user #{user.login} tried to login from '#{request.remote_ip}' while last ip is '#{user.last_ip}' at #{Time.zone.now}"
         return false
       end
       unless user.last_ip
diff --git a/app/controllers/heartbeat_controller.rb b/app/controllers/heartbeat_controller.rb
--- a/app/controllers/heartbeat_controller.rb
+++ b/app/controllers/heartbeat_controller.rb
@@ -26,6 +26,6 @@
 
   def index
     @hb = HeartBeat.where("updated_at >= ?",Time.zone.now-2.hours).includes(:user).order(:user_id).all
-    @num = HeartBeat.where("updated_at >= ?",Time.zone.now-5.minutes).count
+    @num = HeartBeat.where("updated_at >= ?",Time.zone.now-5.minutes).count(:user_id,distinct: true)
   end
 end