In the world of Search Engine Optimization, hijacking is when one website convinces a search engine that the website of a competitor exists at their URL using either a 302 direct. Hijacking is often done for the express purpose of stealing a competitor's search engine ranking.

Say for example that your website is doing great. It's got all the right search engine optimizers working for it and it's ranked number one for a few keywords. You decide to check up on your site's traffic and see how it's doing, expecting everything to be going smoothly, but instead find that your search engine traffic has plummeted. You search Google for those keywords you were ranking so well on, and find that your site has totally disappeared from the search engine results pages (SERPs).

Either you've been penalized, which is unlikely in this scenario since you were doing all the right things, or you've been hijacked by a competitor's 302 redirect, which is an HTML command that automatically reroutes web traffic from one website to another.

Normally, 302 redirects are meant to indicate that a site has only temporarily moved to another URL. The original site still sits in the search engine's index, but the new page's content and link equity gets attributed to the old one.

However, it can also be used as a way of hijacking another site's search ranking. A competitor creates a doppelganger page that has scraped content of the site they're going to be hijacking, and 302 redirects the dummy site to the original, tricking the search engine into thinking that the ranking page is only the temporary version of the doppelganger. The search engine then gives away the ranking and link equity of the original site to the doppelganger hijacking it.

Though search engines are aware of the hijacking problem, and have put preventative measures into place, it still happens. In order to guard against this blackhat SEO tactic, webmasters should search snippets of their page's text in quotation marks, which tells the search engine to search for that text as is, and pull up copycat results.