Would it help to get rid of them and save your valuable time if you change the name of the particular thread they are spamming. I guess the spammers are set up to automatically target the keywords in the thread title.
Nope - they aren't targeting keywords, they are targeting whole websites.
This is not a random thing - there is software you can buy specifically designed to spam forums.
Some people are using it in a very broad way, targeting any site, while others are being very specific in the sites they are targeting (sites with high Google rankings and such).
There is a second class of spammer who actually pay humans to post spam. There are lists of forum sites and blogs with open comment systems which are targeted based on specific topics. Once you get on one of these lists, you will see a lot more spam.
We geo-block a large number of countries, plus we have certain other checks that happen at registration time, which together block about 99% of the spammers from being able to successfully register.
Then we use an anti-spam service which checks the content of posts and identifies which are likely to be spam, this has so far caught about 99% of the spam posts made by people who actually succeed in registering (or were sleeper accounts, registered months or years before we set up the registration checks).
Almost no spam is getting through to be visible on the site now - all you are seeing is the aftermath of those few posts which are made, but are automatically blocked by the software and subsequently deleted by the moderators. Ideally, we'd be able to automatically hide these deleted posts from members, since there is no value in knowing that they exist (unlike valid posts from real members which were deleted for other reasons).
I've seen other sites where bots have managed to get in and posts literally thousands of spam posts within a short period of time. We get a couple of automatically blocked posts each day - so it's really not much of a problem for us at the moment.
... and the moderators are doing a great job of cleaning up those few posts which do get through.
Just to give you an idea about the scale of the spam attacks and the war we are fighting behind the scenes ... there are currently over 36,000 "registered" users on the site.
Of these:
750 have had their account disabled because their email address is no longer valid
2,000 haven't activated their account
2,400 have been manually banned by moderators for posting spam
12,500 have been automatically blocked from completing the registration process
From the remaining 20,000 registered users, I estimate there are probably several thousand bogus accounts that were never used to post spam (and hence haven't been banned yet). We have an automated process working its way through that list and checking to see how many are still valid accounts and disabling those which aren't.
I just checked my logs, we've had over 350 attempted registrations on the site so far today in the 8 hours or so since midnight. Of these, three were legitimate users.