Negative SEO involves malicious practices aimed at harming a competitor's search engine rankings. Tactics can include building spammy backlinks to their site, scraping their content, or creating fake social media profiles to damage their reputation. It's a controversial and unethical approach, and search engines like Google have measures in place to protect websites from such attacks. However, it's important for webmasters to monitor their link profiles and report any suspicious activity to maintain their site's integrity.