I started a forum, soon the forum was spammed with many links. I think with seonuke. More over my site has more than 40000 backlinks because of these spam. I deleted all those spam posts. Will this backlinks affect my site ranking.
This has happened to me too. So what you have to do is have a good anti spam system in place. Make sure you clean up all the spam first then add a good captcha system that will only allow human submissions, moderate your forums well. Links will go all onto 404s when the original content is removed so dont worry about it over time backlinks will be dropped. but maintenance is huge when you are owning a forum.
It all depends on how quickly you got rid of them. I reckon Google have built into their algorithms a check for how long the spam stays. You can't help getting it, you can be judged on how quickly you remove it. To stop it happening again look at how you have akismet configured, moderation for new members, flood control, the ability to post with links (limit to established users). Consider some of the "tricks" used here - things like not allowing new users from a particular ip if someone has been banned on that ip in the last 30 days, or requiring facebook to create a new account. dp still gets spammed but it helps
Thanks, I deleted all the spams after 1 month. Now the forum is clean. Now i manually approve new users.