How to block these Human Spammers?

[induslady]

Ours is an Online Community for Indian Women.

Of late, for the past couple of weeks we have these spammers (humans NOT bot registrations) spamming our forums, particularly a local forum, with "Call Girls" info.

We are fighting hard to crack a way to keep these spammers away. The problem is they are not posting any external links, so that they will get auto-moderated and thrown way.

They are not following any particular email/username pattern in their registrations for us to ban registrations coming from such email.

Also, they have floating IPs, so not able to ban by IPs too. In fact, if we block the IPs they come from, many genuine users will get thrown away because they seem to share the IPs in that network. Also most of the time their IPs are our CDN (content delivery network) IPs.

The ONLY pattern we see is the word "call girls", "escort" and they are mostly targeting one specific local forum we have.

If I block these texts, they are only going to make these text/phrases to change into **** in the posts. But in no way going to prevent the posts.

Quite challenging spammers!!

Is there a way to block them and completely keep them away from our site's forums?