One of the worst experiences for a website owner is finding out that the search results for your site have turned into a pharmacy, a fashion outlet, or even a porn dump.
Those unwanted keywords are a result of Search Engine Poisoning (SEP) attacks. This blackhat SEO technique is used by attackers to take advantage of your rankings on Search Engine Result Pages (SERPs).
One of the ways that hackers avoid being noticed is to hide the spam content from normal visitors.
Source: Security Bloggers Network @ February 20, 2017 at 08:56PM