I am the creator and maintener of the largest site in Israel about woodworking
Like many other sites that allow user generated content, this site has the problem of spam. constant spam. Bad players try to gain SEO, or just maliciously use scripts/bots to register to sites as "real" users and then go on to post garbage on the site. Users on this site are forced to encounter these (sometimes offensive) content, and administators and moderators are in an endless effort to block spammy IP's, delete posts and apologize to their users for any post that stays up for more than a few minutes.
Over the years (site has been active since 2006) I have evaluated many solutions offered, built in plugins, CAPTCHA and more, and eventually someone suggested CleanTalk.
CleanTalk is a cloud based service (SaaS) that takes it upon itself to block all these SPAM attempts seamlessly, without bothering the site operator or legitimate users, seriously, its like magic! In over a year of using CleanTalk, I have not seen a single spam message in my board, and only in one case a valid post was denied (a case of a fresh user posting a few seconds after registration, and using some keywords in his message that were questionable). And due to CleanTalk's excellent monitoring and logging dashboard I found the problem immediately and fixed it in a manner of minutes.
Once you open an account and install/integrate the solution into your site, you will not see anymore spam. You get a 14 day trial, and if you need more time just ask their customer service, or even purchase a plan, there is a 60 day money back guarantee if you are not happy – and you will be. Also they offer various plans with the common denominator – sensible, affordable pricing. By number of sites, or by traffic (number of spam checks per month).
They provide working plugins/addons for most CMS/Forum software out there and SDK for Mobile Apps and Libraries for many popular programming languages (if you want to roll out a custom integration).
I cannot recommend them enough, 5/5 stars! Try CleanTalk today, you won't regret it!