Disabling links in first posts for new members, how?

[LoreleiWeb]

Hi all,

this is my very first here, so I apologize if it will end up in the wrong section. I searched the forum before posting yet found no answer... (I know, I know, probably didnt search good enough )

I'd want to disable link in new members posts, say, for the first 5 posts they make, as normally spammers don't make more than that anyway.

I have a nice daily amount of porn and scam links posted, as well as those who "submit their site for a review" and I'd want to put an end to it. I have seen it in other forums, so it's probably a hack / mod.

Thanks in advance.

I asked the same question on vbulletin.com, but they said it's a manual code modification for which I can get support here...