diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 41d1d44..d27b719 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -2,6 +2,8 @@
 
 # Forma de ingreso a Sutty
 class ApplicationController < ActionController::Base
+  include ExceptionHandler
+
   protect_from_forgery with: :exception
   before_action :set_locale
 
@@ -17,10 +19,13 @@ class ApplicationController < ActionController::Base
 
   # Encontrar un sitio por su nombre
   def find_site
-    current_usuarie.sites.find_by_name(params[:site_id] || params[:id])
+    id = params[:site_id] || params[:id]
 
-    # TODO: reenviar a un 403 si el sitio ya no está permitido para le
-    # usuarie
+    unless (site = current_usuarie.sites.find_by_name(id))
+      raise SiteNotFound
+    end
+
+    site
   end
 
   def find_post(site)
diff --git a/app/controllers/concerns/exception_handler.rb b/app/controllers/concerns/exception_handler.rb
new file mode 100644
index 0000000..3be8412
--- /dev/null
+++ b/app/controllers/concerns/exception_handler.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+# Gestiona las excepciones que lanzamos desde los controladores
+module ExceptionHandler
+  extend ActiveSupport::Concern
+
+  class SiteNotFound < StandardError; end
+
+  included do
+    rescue_from SiteNotFound, with: :site_not_found
+  end
+
+  def site_not_found
+    redirect_to sites_path
+  end
+end