Most people think of SEO as a "white hat" activity - meaning that it's the process of optimizing a website for Google's search engine algorithm in a way that complies with the search engine's guidelines. However, there is also a "black hat" approach to SEO which refers to any tactics that violate those guidelines - such as spamming links, keyword stuffing, and creating fake social media profiles. Negative SEO is simply the act of using black hat techniques to harm another website's ranking in Google's search results. This can be done by targeting that site with negative backlinks, or by artificially lowering its PageRank score. While it may not be illegal, it is certainly unethical, and it can have serious consequences for the victim website. If you suspect that you're the victim of negative SEO, the best thing to do is to reach out to a professional SEO consultant or SEO agency who can help you clean up your backlink profile and recover from any damage that has been done.