Unblock user

gistfile1.php

/*
 * Implements hook_user_operations().
 *
 * Creates an action to unblock a user and additionally remove information
 * related to past login attempts.
 */
function mymodule_security_user_operations() {
  return array(
    'unblock_and_clear' => array(
      'label' => t('Unblock selected users and clear failed login attempts'),
      'callback' => 'mymodule_security_user_operations_unblock_and_clear',
    ),
  );
}

/*
 * Bulk user operation to unblock a user (and remove all failed login attempts).
 *
 * The standard Drupal unblock operation doesn't affect the flood table and
 * login security state.
 */
function mymodule_security_user_operations_unblock_and_clear($accounts) {
  $accounts = user_load_multiple($accounts);

  foreach ($accounts as $user) {
    _login_security_remove_events($user->name);
    _mymodule_security_remove_login_flood($user->uid);

    // set user status to 1 (active, not unblocked)
    $user->status = 1;

    user_save($user, array('status' => 1));

    $message = t('User <strong>%name</strong> has been unblocked', array('%name' => $user->name));
    drupal_set_message($message);
  }
}

/*
 * Remove login flood information from the DB.
 */
function _mymodule_security_remove_login_flood($uid) {
  db_delete('flood')
    ->condition('event', 'failed_login_attempt_user')
    ->condition('identifier', $uid . '-%', 'LIKE')
    ->execute();
}