Unfortunately there are too many modules that provide CAPTCHA-free spam protection. Some of them look like deprecated, some - have even more than BOTCHA number of installations. It would be nice if we could join the forces - and work together on a single project. "Collaboration, not competition", as you know.
Here you are a list of similar projects, that I am going to merge into BOTCHA:

I also liked (as ideas for new recipes and new functionality to implement):

Comments

Issue summary:View changes

Added Honeypot issue.

I reviewed Hashcash module code. It implements one recipe that fits exactly into what Botcha does. I think Botcha will benefit if Hashcash recipe is added. The advantage of Hashcash recipe is in straining CPU of client PC for each form submission. Normal users won't notice the time it takes (a second or so of hashcash computation time), but spambots will be hit hard and will reduce their submissions by 100x.
One interesting idea of Hashcash (besides the recipe) is a fallback on Captcha module if client does not have javascript. But we know Captcha's today are completely broken by spambots, so I'm questioning value of that feature.

Issue summary:View changes

Added Spamicide issue.

Something to think about:

See https://drupal.org/node/1959310.

I've proposed an anti-spam module framework. Instead of merging a lot of anti-spam techniques and services into a single monolithic module, I propose that there be a pluggable/hookable framework that allows independently-developed modules to register, then they can all work together.

So, you could select from your favorite detection modules, your favorite blocking modules, your favorite reporting modules, and your favorite cleanup modules, and they'd all automatically work together via the same API.

That way, the different anti-spam modules don't have to keep re-inventing the wheel, where each one has it's own different detection, blocking, reporting, and cleanup subsystems. Just plug in to the anti-spam framework, and you get all the features from the other modules.

Issue summary:View changes

Added Hidden Captcha issue.

@DanZ Sorry for answering so late - I hope not too late. :)
I like the approach. It is definitely the way to move on.

"Grand Central Bad Behavior Blocker" (GCBBB)

- ha, looks nice! Could be just "Censor" or "Advisor" or "Validator". Under consideration.
So, as you described in https://drupal.org/node/1959310 there should be several parts, that are going to play together, each of them simultaneously could be extended by any other contributed module:

  • Detecting unacceptable behavior: it could be spam posting, filthy language, IP that is out of some range - the types of such things could be defined outside of the GCBBB module.
  • UI for dealing with unacceptable content - and UI for defining "the rules of acceptance". In my view "the rules of acceptance" imply "sources of spam" mentioned by you. They could be extended outside as well: including reporting of such unappropriate behavior to some external "services".

Am I missing something? I think the level of abstraction fits. This is the way to become "Huston" for all of the diversity of spam-and-other-bad-things-protection modules, isn't it?

Issue summary:View changes

Added Badbot