The SEO industry has two groups – one ‘value’ group and the other ‘numbers’ group. Former uses quality and latter uses buying links, spamming etc to gain page ranks. Google’s Penguin update discouraged number strategists by compelling adherence to Google Webmaster Quality guidelines. Ranks of ‘number’ strategists were reduced. However, negative SEO, meaning attacking competitors’ websites by buying spam links, is a challenge. The best protection from such attacks is to check the Webmaster Tools account for an abnormally high number of incoming links and random IP addresses linking. Check their age, patterns and sources and inform Google about the changes you’ve seen. Bing’s Disavow Links tool also allows exclusion of spam links.
Read the full article here:
How to Protect Your Site from Link Spam and Negative SEO – Search Engine Journal