Captcha showing up when posting

For the first time today, captcha was required on our board in posts, triggered by this thread: I AM ROBOT.

Upon investigation at our host's forum, I discovered that it is triggered by certain words or phrases to prevent spambots or scammers. So far, at least 3 posts in that thread have triggered it! So that is what is going on; I am trying to find out if that feature can be disabled. Our host added it and enabled it on all boards without telling anyone, as they do with new features from time to time.

It looks like this feature is global and can't be turned off. Some experimenting with it on our host's forum revealed substituting an * for letters won't avoid triggering captcha either.