Well, today I received about 70 Submissions by spamming my Directory and about 30 Website Comments from the same Source. Nothing "bad" happened so far, because all the submitted Links were classified as "suspended", which is a good thing 
But I dont like it, I have a bad feeling about it. I guess something will happen in the near Future. Dont know what, but I think those Guys are trying something special.
Or maybe its just Paranoia 
So, ok, I did try it again with the code submitted by esm, thanks by the way, your help is very appreciated.
I added the Code you posted here in line 380 (about) like this:
Code:
/*===================================================
main
===================================================*/
function check_origin() {
return ($_SERVER['HTTP_REFERER'] == "http://" . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF']);
}
if ($pflag == 'add' && check_origin()) {
ProcessFormAddUrl();
}
else {
ShowFormAddUrl();
}
include "application.php";
RunPreFilter(__FILE__);
if ($only_registered_can_add_link == 1) {
ExecuteFilter("validate_user");
}
if ($require_visit_category && empty($cat)) {
DisplayTemplate($theme_path . "add_error.html");
RunPostFilter(__FILE__);
}
else {
//get all id
$category_obj = new clsCategory;
$category_obj->table_name = "idx_category";
$arr_cat = $category_obj->GetChildren(0);
$dummy = array_shift($arr_cat); // remove 0
if ($require_visit_category && !in_array($cat, $arr_cat)) {
DisplayTemplate($theme_path . "add_error.html");
RunPostFilter(__FILE__);
}
}
if (!empty($cat)) {
// get category permission
$query = "select permission from idx_category where category_id = '$cat'";
$result = $dbConn->Execute($query);
$permission = $result->Fields('permission');
if ($permission == 2) {
DisplayTemplate($theme_path . "add_not_allowed.html");
RunPostFilter(__FILE__);
}
}
if (empty($pflag)) {
ShowFormAddUrl();
}
elseif ($pflag == 'add') {
ProcessFormAddUrl();
}
RunPostFilter(__FILE__);
?>
A thing I really dont know about is the rest of the Code? Is it correct that I add it between the original Code? In original it starts like this in line 380
Code:
/*===================================================
main
===================================================*/
include "application.php";
RunPreFilter(__FILE__);
if ($only_registered_can_add_link == 1) {
ExecuteFilter("validate_user");
}
if ($require_visit_category && empty($cat)) {
DisplayTemplate($theme_path . "add_error.html");
RunPostFilter(__FILE__);
}
else {
//get all id
.....and so on.
Or do I have to do something else? I am not a PHP Coder Guys, so please understand and be nice 
Thanks