Cake2でURL直打ちでのアクセスを拒否する

画面上で非表示にしているが、データがあるためURL直打ちだとアクセスできてしまうことがあるので、それを防ぐ方法。

Controller

public function detail($id = null) {
       $conditions = array('Model.delete_flag' => 0);

       if (!$this->Model->exists($id, $conditions)) {
          $this->redirect(array('controller' => 'home', 'action' => 'index'));
       }
}

Model

    public function exists($id = null, $additionalConditions = null) {
        if ($id === null) {
            $id = $this->getID();
        }
        if ($id === false) {
            return false;
        }
        $conditions = array($this->alias . '.' . $this->primaryKey => $id);
        if ($this->schema('delete_flag') != null) {
            $conditions[$this->alias . '.delete_flag'] = 0;
        }
        if ($additionalConditions !== null && is_array($additionalConditions)) {
            $conditions = array_merge($conditions, $additionalConditions);
        }
        return (bool) $this->find('count', array('conditions' => $conditions, 'recursive' => -1, 'callbacks' => false));
    }