Sticky How to protect my forum from spam

So I got a really annoying problem. As we all know there are still some retarded people out there that think that spamming 1000s of sites out there using bots will make them rank better in google, so thats what they do.

Now I quickly figured out how to shut them out, replacing the default captcha with a different one.

But the main problem is that the bots keep thinking, that they posted something, and keep building 100s of bad links to my site every day. Im at about 50k links form really low-quality places all over the web.

95% of those links point to:
ROOT/forum/newtopic

What can I do to stop this. The bots are not able to sign up, but they still keep building shitty links to my site... WHY???

I'm quite afraid that all these thousands of bad backlinks are going to hurt my SEO.

I'm quite sure it has something to do with the structure of Kunena. I never had this problem with other joomla extensions, phpbb, vbulletin, Fireboard and other boards.

Thanks for everything
Kunena is awesome!

//edit:
I know that they are XRUMER, because one of them was advertising XRUMER^^

*** Topics merged ***

G'day, XRUMERbot, and welcome to Kunena.

Kunena is no more or less susceptible to attacks from XRumer than any other web-based discussion forum on the internet.

Is Kunena software designed to produce spam ?

Do you have evidence that Kunena produces spam? :huh:

Why all use recaptcha on joomla and forums? Bots are easy register with recaptcha enabled.
For years i am use on my joomla and on my forum security question.
For example i make my own question - who is the best humans friend, in russia we say that its a dog. In my question i am use letters from different languages, mixed with russians. So even if a poor indian guy (who usually solves the captches for one cent)will insert this question in translator -he will not get it translated.
So for the last 5 years i didnt have even one bot registered or spam post posted.
For Kunena and Joomla there is only one extension which work like charm. Tomorrow i will post it here.
I do not ask my users even to register to post. In the end of the post creator window there is my question, without answer u cant post. So easy. Users hate captches and its really slow down forum grow.

Can you imagine if every site will use its self question? This will make it almost impossible to spam in internet. Even for soft like xrummer.

Ok people, instead of use captcha, use EasyCalcCheck Plus - ECC+ for security question on joomla registration and Kunena posting (without registration)
Read my previus post. Stop use captcha, this is 21 century for God sake