Yes, but at the moment only stored in my memory: bots access the sites and serve a human the captcha who finalizes the entry. The bot populates all the fields + a zillion spam-urls. The humans usually sit in countries like China where man power is really cheap and do nothing all day long but solving captchas for 70 bucks per month - eyes squared inclusive.
So addressing the access might not be even half of the necessary action - IP-blocking is pretty useless. For one, IP's change frequently, two: sometime a college, university, a whole region share an IP. A spammer or troll will not be deterred.
So what needs to be done additionally is to scan the content of the comment for formal criteria such as multiple urls. I can conceive of a user leaving 2 or 3 urls for reference (though unusual) but more than that?
So I repeat my question: why doesn't Akismet catch the culprit? With a Wordpress blog, it surely would sort out these comments...
some quick googling:
ha.ckers.org/blog/20080311/human-captcha-breaking/
www.freelancer.com/projects/by-tag/human-captcha-break.html
en.wikipedia.org/wiki/CAPTCHA
"Human solvers
CAPTCHA is vulnerable to a relay attack that uses humans to solve the puzzles. One approach involves relaying the puzzles to a group of human operators who can solve CAPTCHAs. In this scheme, a computer fills out a form and when it reaches a CAPTCHA, it gives the CAPTCHA to the human operator to solve.
Another variation of this technique involves copying the CAPTCHA images and using them as CAPTCHAs for a high-traffic site owned by the attacker. With enough traffic, the attacker can get a solution to the CAPTCHA puzzle in time to relay it back to the target site.[20] In October 2007, a piece of malware appeared in the wild which enticed users to solve CAPTCHAs in order to see progressively further into a series of striptease images.[21][22] A more recent view is that this is unlikely to work due to unavailability of high-traffic sites and competition by similar sites.[23]
These methods have been used by spammers to set up thousands of accounts on free email services such as Gmail and Yahoo!.[24] Since Gmail and Yahoo! are unlikely to be blacklisted by anti-spam systems, spam sent through these compromised accounts is less likely to be blocked."