You can change the behavior of user login functionality. You may deny the login based on any factor. Default hook value is `true` mean allow login.

function my_component_init(){
ossn_add_hook('user', 'login', 'my_component_hook');
function my_component_hook($hook, $type, $return, $params){
//$params['user'] contain the user instance
if($params['user']->username === 'abcdef'){
return false;
return truel
ossn_register_callback('ossn', 'init', 'my_component_init');

This example will check if username is abcdef then don't allow login otherwise if any other username allow login.

User login