I've been receiving spam in my support forum. It wouldn't even be for the same thing either. It would always be something different and random. So far I have banned the IPs that have posted it and increased my forum's spam filter, but I'm almost positive it'll come back. Any ideas on what I can do?

what forum software is this? add recaptcha or something.
if you use mybb, it supports Akismet checking for every single posted message.

its PhpBB3

do you have captcha enabled? search phpbb's forums for some antispam plugins

Install a decent CAPTCHA that includes some distortion in the image (so it cannot be read easily via OCR techniques) and you should be able to cut out most of the spam.

These spammers never stop now using OCR to continue spaming geez.

I would recommend adding a Anti Bot Question (http://www.phpbb.com/community/viewtopic.php?f=69&t=645075) to your phpBB3 forum. I run a personal forum for a small game community and I have never used a CAPTCHA. However, I have used a Anti Bot Question and so far it has worked wonders. In just over 18 months, we have had not 1 single spammer register.

Good Luck!

I second the suggestion of using an antibot question. That with recaptcha won't be perfect, but will do wonders to keep the cruft from your forums.

Most of forum customers we host have both setup and find the slightly longer registration a fair trade for reducing spam. Another suggestion is to make the Anti Bot question relevant to the forum if possible as most forums employ a very simple math problem.

Here's a Fancy jQuery Captcha (http://www.phpbb.com/community/viewtopic.php?f=69&t=1795905) that I have not yet personally used.

I highly recommend installing/configuring mod_security as well, which can do a great job stopping some bots.

Use the simple MOD for phpbb that will stop from adding new members to the member's list until approved by Admin. But anyone clicking on 'latest member' will see their profile.

A simple Idea would be to ban the ip for ever....