What is URL hijacking and how can you prevent it?

URL hijacking can cause your website to be deleted from the index of a search engine and hidden from potential visitors. This phe­nomen­on commonly occurs when redirects are used instead of links.

What is URL hijacking?

The concept of URL hijacking describes a phe­nomen­on wherein a website dis­ap­pears from the results of a search engine and is replaced by another. This other site links to the actual target page or URL using a redirect. For example, linked-site.com links to your-site.com but uses a redirect instead of the usual HTML tag <a>. The re­dir­ec­ted URL looks similar to the following example:

www.linked-site.com/redirect .php?target=www.your-site.com

When a search engine finds a link like this, it cat­egor­ises the linked site and the target site as identical, which means that it deletes one of the two from the index. It orients itself based on HTTP status codes, which attach to the redirect.

While Code 301 (Moved Per­man­ently) denotes a permanent re­dir­ec­tion from the given URL, Code 302 (Found) denotes a temporary re­dir­ec­tion to the des­ig­nated URL. The first type is un­prob­lem­at­ic, but the 302 redirect is the main reason for URL hijacking. These well-made redirects suggest to the search engine’s crawler that the target site is only temporary and that the linked page is actually the original – and the crawler never checks whether the sites are actually related or not. If this isn’t checked, the wrong page is indexed and takes on the ranking of the linked URL.

When are 301 and 302 redirects used?

There’s a wide variety of reasons for using URL re­dir­ect­ing. As a result, permanent re­dir­ect­ing of typo domains to the correct domain are a wide­spread practice. For example, if you ac­ci­dent­ally type googel.com instead of google.com into your browser’s address bar, you will still be taken to the popular search engine’s start site. Permanent re­dir­ect­ing to the correct address of the main page is also not unusual.

If you visit the main page of the English-language version of Wikipedia, for example, by typing in en.wikipedia.org, you will be taken to en.wikipedia.org/wiki/Main_Page via a 301-redirect. De­velopers also use permanent re­dir­ect­ing to lead visitors to the new web address after a domain change or to identify the content of a web project that has received a new URL.

Temporary 302 redirects, on the other hand, are primarily used to tem­por­ar­ily display content from another URL so that it remains available, for example, if the original page is un­der­go­ing main­ten­ance. If a developer manually creates this type of re­dir­ec­tion, the intent is that the content will appear on the original URL again later. There are three temporary redirect scenarios that can lead to URL hijacking, one of which is in­ten­tion­ally used for this purpose:

Un­in­ten­tion­al use of the 302 redirect

It is quite possible for de­velopers to link to a different web project with a temporary redirect without having bad in­ten­tions. It could be a mistake where they intended to set a permanent redirect. The URL rewrite engine of the Apache webserver, mod_rewrite, sets default redirects with the 302 status code.

Dy­nam­ic­ally generated URLs

PHP is a widely used scripting language for web de­vel­op­ment. The server scripts in this pro­gram­ming language are a simple and practical way to create dynamic content for your website. But often times these are also PHP scripts that dy­nam­ic­ally integrate target addresses into an existing URL using the temporary for­ward­ing status code 302. These types of scripts are mainly used in web address dir­ect­or­ies, but also in many content man­age­ment systems.

In­ten­tion­al URL hijacking

Criminals also know how to use URL hijacking, and they gladly make use of it. They con­sciously use 302 redirects to advance their own content in the index and to ‘kidnap’ par­tic­u­larly well-ranked pages. The tactic is neither sus­tain­able nor legal and it falls under the term black hat SEO.

URL hijacking vs other attack methods

URL hijacking is often confused with other attack methods such as domain hijacking or ty­po­squat­ting. These are actually different types of attacks that can be used to harm you or your website’s ranking.

URL hijacking vs domain hijacking

Although both URL hijacking and domain hijacking are used with the aim of gaining control over a website, the two attack methods differ, es­pe­cially when it comes to their approach:

Domain hijacking is when attackers gain control over a domain by accessing the domain man­age­ment accounts, for example, by changing the DNS settings. In the worst-case scenario, attackers can take over the victim’s entire web presence.

URL hijacking vs ty­po­squat­ting

As the name suggests, the attack technique ty­po­squat­ting takes advantage of typos. Where redirects are normally used to help the visitor get to the desired website despite minor typos, this is where ty­po­squat­ting sneaks in. Attackers purposely register domains with common typos to direct visitors to their website, which often contains malicious code.

How to protect your website from URL hijacking

Website operators trying to improve the ranking of their website know how chal­len­ging and time-intensive the process is. The higher you rise in your search engine rankings, the more likely your indexed pages are to get hijacked. Unlike an attack that happens due to security gaps in a web project, the process of URL hijacking is closely linked to the basic SEO dis­cip­line of link building, so it can’t just be prevented by using antivirus software.

As a result, it’s in­cred­ibly important to regularly analyse both new and existing backlinks to filter out prob­lem­at­ic URLs. There are a number of tools and services you can use for this including:

• SEMrush
• LinkRe­searchTools
• SISTRIX
• Google Search Console.

Google provides a tool for removing URLs that allows you to delete any unwanted redirects that link to your website from the search index. Before doing so, you should always contact the website ad­min­is­trat­or re­spons­ible for the site and ask to adjust the routing. This way there’s a chance to keep the cor­res­pond­ing backlinks. The status code 307 (Temporary Redirect) has an option for temporary for­ward­ing that doesn’t lead to URL hijacking, which has been available since HTTP 1.1. If the original site is already missing from the index, you should contact the search engine provider and ask for a res­tor­a­tion of the original rankings once you’ve reworked or deleted the damaged backlink.