I've sent a message to Calli (I think - not 100% certain as I get 404 when I try to load his profile page) to ask about status of moderator permission thing & about possibly implementing captcha solver for people with less than 10 or so posts.
This site already has a captcha for its registration form. Its that google "nocaptcha" thing where you only click "Im not a robot" and it checks a lot of stuff with an complicated algorythm if your browsing behavioir is more like a bot or human.
So human spammers will pass through even if you make another captcha when posting something in the topics or create a new one.
On my (old) website + Minecraft community forum I implemented a normal captcha with random questions regarding the site or minecraft server (whats the name of the server, how many cities can you join,...). That made it to complicated for these spam people to deal with finding information on the site. A normal user who wanted to join the forums anyway had no problems answering these...
We also checked the entered emails at registration against spam list servers and blocked a lot of (trash) email providers in the first place.
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Another possibility to prevent these is to check the entered title/post strings against a list of typical spam post text blocks like we saw lately.
A post with "free passports, etc" for example gets queued and needs to be checked by a moderator / admin