Thanks guys for your replys.
@ Simon, I have done this: 'make new registrations only able to post in one forum' & added stopforumspam mod, that stops all the viagra spam
Theres also a lot of members that use a multi poster to post their threads to a lot of sites with one click, so im trying to block them aswell. Im pritty shore they've been coded to use newthread.php to post, so thats why i want to rename the file name.