Jetpack_Protect_Module::check_preauth PHP Method

    function check_preauth($user = 'Not Used By Protect', $username = 'Not Used By Protect', $password = 'Not Used By Protect')
    {
        $allow_login = $this->check_login_ability(true);
        $use_math = $this->get_transient('brute_use_math');
        if (!$allow_login) {
            $this->block_with_math();
        }
        if ((1 == $use_math || 1 == $this->block_login_with_math) && isset($_POST['log'])) {
            include_once dirname(__FILE__) . '/protect/math-fallback.php';
            Jetpack_Protect_Math_Authenticate::math_authenticate();
        }
        return $user;
    }