It seems the new functionality I added is working wonderfully. In the days since Sunday I've had no spam comments posted (touch wood) although there has been over 500+ hits from possible spammers.
It's quite funny that the spammers browser information indicates that they are using Java to run these automated spam scripts and there is no attempt to hide this fact. The worst offender on my website in the past 4 days was from a network in America registered to “AirlineReservations.Com, Inc.”. Which it turns out is a dubious natured website, mostly comprising of adverts.
A quick scout around revealed that this IP is indeed frequently responsible for spamming guestbooks and comment sections of websites all over the place. So as a further measure to reduce the number of bots that will be able to post spam comments I've been looking at an additional measure that I can implement. I've been following Project Honey Pot and schemes like it for sometime so I've decided to use one of their services, http:BL.
This blacklist service can be used to check the IP address of a visitor against the data held by Project Honey Pot. This will return 4 pieces of information:
A valid query response
The number of days since the IP was last active on the Project Honey Pot network
A Threat Score
And a type of visitor indicator
Using the last 3 pieces of information it should be possible to reduce potential spam attacks even further.
Well I've added new functionality to the comment pages that will now check against the blacklist. I'll monitor the traffic for the next week or so just to check that all is ok.