Negative SEO is taking away the sleep of keen marketers. It simply creates tensions for them as it can reduce their website’s ranking in the search engines. Common type of negative SEO that is being the hot topic to discuss is the link based negative SEO.
Google is quite unwavering about no existence of negative SEO. However it also admits that negative SEO via link building is a possibility. For this Google is putting efforts to make sure that any competitor could not hurt your website rank via link building. It has built in things into their algorithms to determine whether the links are self-made or not.
It is however also that not everyone has to be worried about the negative SEO. Some weird looking links are basically not the Negative SEO. It is also shocking that some of the SEO building companies have been building them unnatural links. Even not all cases of hacked sites are negative SEO.
Some of the examples that you can consider as negative SEO are links from foreign forum, large number of links from complete nonsense blog post, sudden influx of link from Russian sites and of links keyword anchored links from multiple sources. Its better you do regular audits of the links and submit a disavow file.