When Embossed and his/her friends trolled the forum a few weeks ago their damage was limited by the 10 posts per day limit. They weren't very bright as they could have posted as guest(which doesn't have such limit) in any forum. A week later s/he came back and posted while using another nick, I didn't really wanted to see how much time they would take to realize the "guest" user flaw in the system so I made every section available to registered users only.
Between then and now a bot was released that was able to OCR the visual confirmation (captcha) image used to prevent spambots from posting on the board.
So far, some bots are indeed coded to preferably spam in general/test/everything-else forum as their posts are likely to last longer than in a forum with a clear topic. However, if they are not able to post in these general forums, they can and will probably spam anywhere else they can since those people make money if they can put as many link as possible on as many board as possible in order for search engines to put their website at the top of the list. There are few incentives to have a bot spamming in moderation.
To prevent this problem, I made the captcha image more difficult to identify for OCR programs.
<center><table><tr><td align="center"><font><tt>The old image
</td>
<td align="center"><font><tt>The new image
</td></tr></table></center>
Note that B and 8 are similar and difficult to see, but B has a clear vertical line on the left of the letter. Since this captcha is not a standard phpBB feature, bots should be blocked. I have put the permissions on the General forum to allow guests to create new topics so that current spambots can try to break the visual confirmation. If they can't I will allow guest users on all forums but now, the only thing I am not sure of is if I am blocking real people as well.
If you have some free time, try to preview a few anonymous posts in the general forum and tell me if you can identify correctly the visual confirmation (you choose to only preview your post; it won't be added to the board but you will still know if you have entered the right code or not).