had a bit more trawl of php, maybe a mod/admin could scope these out??
TIPS
Set activation to 'user' or 'admin'
This feature sends an activation email to either the user registering or the administrator. Unless you plan on activating all members personally, you should leave this set to 'user'. Many bots use fake emails when registering, so this will stop them from activating the account. It will also discourage some human spammers, since they will need to provide a valid email account each time they register. Not only does this stop some spam, it also helps make sure that all members have valid email accounts on file (which will prevent emails from bouncing back when you send mass emails). You can activate this option in the 'configuration' section of the administration panel.
Enable visual confirmation
This is the image with the numbers/letters you had to enter into the box when registering on this site. While doing nothing to prevent human SPAM, it should block most of the bots. This feature has been improved in recent versions and even further improvements are in the CVS (will be in the next release). You can activate this option in the 'configuration' section of the administration panel. If you are using the latest version of phpBB, but do not see this option in the administration panel, your template is likely out of date. See this article by espicom for more info and the fix:
http://www.phpbb.com/kb/article.php?article_id=329.
1. Disable guest posting
If you allow guests to post, SPAM bots will not even bother registering. It is therefore generally recommended that you disable guest posting on your board (
http://www.phpbb.com/support/guide/#section3_1_2_1). If you absolutely must allow guests to post, I suggest you install the Anti-bot Guest Post MOD (#2 below) by otseng or the Visual Confirmation for Guests MOD by Kanuck (#15 below).
MODS
http://www.phpbb.com/phpBB/viewtopic.php?t=210055 Checks the amount of time it took to submit the registration form. If it is less than 5 seconds, the form cannot be submitted.
http://www.phpbb.com/phpBB/viewtopic.php?t=383305 This MOD replaces the standard visual confirmation with a question selected at random from a pool. You may add custom questions to the pool, which makes this MOD very dynamic.
The "how to install a MOD bit :
http://www.phpbb.com/kb/article.php?article_id=150