Help fight ddos with this mod thats needed!!!
 

Have a mod that does two things. If activated, One it gets all ips that register users have used and only allows them, blocking all other ips via .htaccess.

Or

You can turn on the 2nd part, giving each guest only 5 reloads max, then ip is added to ban list of .htaccess (for private forums)

Actually this is an interesting concept worth taking a look into. Defiantly not thought about doing something like this and it would leave the DDOSer thinking. From my experience its usually a disgruntled user that is the one DDOSing but i will take a look into this.

If it blocks all other IPs via .htaccess, then how would new users ever be able to register?

I think he is talking about using it for a short time say when he is getting DDOSed it will give him time to track down who is DDOSing his site while not effecting current members. This will allow the website to maintain as normal as possible while being DDOSed.

You don't fight a DDOS in the end-user application (vBulletin). A DDOS is best mitigated on the network or O.S. level.

now, a mod that after a certain amount of refreshes in a short period added an ip to iptables... that would be interesting (even better if it added it to the iptables of a router upstream of the server)

Again, that should be done on server level, not in the application layer.

Any code that you would add to the application will only increase server processing for each page, resulting in only more problems.

A DDOS should be mitigated before it even reaches the application (ie. vBulletin).