Important, please read! Changes in user groups and permissions.

[Moses]

Then just put the site under https://cloudflare.com/. It's free, and is excellent to help prevent DDOS attacks. It's not full proof of course, but it definitely helps, to the point it's a requirement for any new clients of mine.

I have my own sites under CloudFlare and can vouvh for it. Again, it's free. You just need to switch the domain's DNS over to CloudFlare's nameservers, and the site will be far better protected against bot attacks. Again, not full proof, but nothing is in the online security world. However, without question it helps greatly.

once again:

It is not a DDoS

[cdnmatt]

Your site, so up to you. You're getting spamed by a botnet, correct? Put CloudFlare on the domain, change the status to "Under Attack", and in 5 minutes the attack will be greatly reduced if not stopped completely.

Again, your site, so up to you.

[Moses]

You're getting spamed by a botnet, correct?

nope... one or few very sophisticated bots, what makes registrations and really emulate human's behavior... Cloudflare helpless in that case... I need to have buffer group where Akismet will kill em... unfortunately forum by default promote everyone to Registered users, so I have to change "Registered Users" group as buffer group and move all real user to another group - it will be "Advanced Users". "Registered Users" group will be honeypot for bots.