You mean avoiding your website to be branded as spam site since some link builders use spams to promote your website? I think, you need to just update the contents of your website into more clear one and promote your site to quality linkers.
The BEST way to avoid spam is to turn off your computer and walk away. Joke aside, I don't understand what you mean by "spam by others wrong link building in our site"???
Sounds like you hired someone to do some SEO work and got the old screw? This happens and at times it is hard to overcome. This is because no matter who did the work you own the site. Building back a good reputation can take time and a lot of white hat SEO.
What exactly do you mean by illegal work. You have a site or forum that other can come to your site and can submit any stuff. If the site is such then there should be a moderator who moderates every posting. If the thread of submission is found irrelevant then he/she has a right to delete.
What did you mean by spam? Do you want to remove comment spam. So if you use wordpress as cms then there are lots of plugin to use like mollom. Thanks
You can have lot of things like the Akismet. Also make sure you control the comments posted on your site. Do not allow spammy comments, it hurts badly.
My view is that you need to build links slowly, don'tsuddenly create hundreds of links overnight. Also don'y but links as google is getting better at spotting link brokers and if your site is filled with links to known spammers then you may be penalised
Your thread have no enough info what actually you're saying. SPAM is now a big issue in internet age. Let us know what kind spam is happening with you site. so plz clear your thread so that we can help you whenever possible.