Spam trap

I seem to have created a spam trap, or, at least, most if it is falling into a black hole.

My preferred spam tool was a Captcha tool that made you rotate an image and only when it was lined up could you post a comment.  That stopped working and would not any comments through so I had to disable it.  As soon as I did so, Woosh! the comment spam starts reappearing.

Most of it gets created against one specific post, for some reason.  Anyway, I had an idea.  I created that post again and gave it a different permalink.  A redirection  from the old permalink to the new was automagically created by WordPress, although I have no idea how.

Now the copy of the page appears but the original version does not.  However, the spam is being posted to the original page; presumably because they are going direct to the /id=nnn link rather than the permalink.

Rather than delete the page and risk the spammers picking a new one to post their spam to, I’ll just leave it there.

What I need now is a WordPress plugin that says “For any comment posted on this page, delete it and blacklist the IP address”.  That would turn my spam black hole into a honeytrap.