Referrer sites are used to send users from one website to another. Referrer URL data is often used by marketing professionals to identify where traffic to their website is coming from. Referrers can also be used to show visitors to a website different versions of the same website depending on whether they have entered via the specific referrer or not.

How do referrer sites relate to Child Sexual Abuse Material?

Referrer sites are sometimes used in an attempt to disguise the distribution of Child Sexual Abuse Material (CSAM) by acting as a "gateway" to the illegal material.

In cases such as this, a website entered via a link on a specific referrer site would display illegal content. If, on the other hand, the URL of the same website is directly loaded into the browser or is entered via a different referrer, then it would display legal content such as adult pornography.

This can slow down the process of removing content because if the report does not include the referrer URL, or “gateway” URL, then the analyst processing the report might only be able to see the legal content. This makes it harder to access and take down the illegal content.

What can be done about this?

If you ever do come across CSAM online, you should always report it. It might not always be obvious if you are being shown the illegal content as a result of entering via a referrer site, but if you suspect that this may be the case, then you can help hotlines get the content removed by including the referrer URL in your report.

If the hotline does not receive the referrer URL, then the process of finding the content can take more time. However, analysts are trained to recognize referrer sites and find referrer URLs so that they can make sure that illegal content on a site is removed. Technological solutions are being developed, which automatically include the referrer when a report is made.

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