Child sitting at desk

Image Hash List

Use the power of tech-for-good to prevent the upload and proliferation of known child sexual abuse imagery across your networks and platforms with the IWF Hash List. 

The IWF Hash List contains a special catalogue of codes, or hashes which is updated daily and manually verified by our expert analysts. Each hash is completely unique. It’s a type of digital fingerprint, or label that identifies a picture of confirmed child sexual abuse. Each criminal image has its own individual hash.

Once an image has been hashed, it can be recognised quickly. Better still, our list of hashes can block thousands of criminal pictures from ever being uploaded to the internet in the first place.

By using our Hash List, tech companies can stop criminals from uploading, downloading, viewing, sharing or hosting known images and videos showing child sexual abuse.

In the battle to defend child victims of sexual abuse online, the development of our Hash List has been a game-changer.

In the battle to defend child victims of sexual abuse online, the development of our Hash List has been a game changer.

Once our analysts have assessed an image or video as criminal, they give it a hash. That hash is loaded onto our Hash List. From there the list can be used by organisations who work with images or videos. As each hash refers to a fully assessed criminal image, that company is able to block the image from being uploaded to its network.

Today, our Hash List contains hundreds of thousands of hashes, or unique digital fingerprints and we add to it daily. We never forget that each one is an image of a real child being sexually abused; an online record of suffering and pain; the documentation of a crime scene and a place of terror for that child.

By using the Hash List, tech companies can protect customers, staff and users from accidentally stumbling on these criminal images. They can help stop perpetrators profiting from their horrific crimes. They can defend victims, the children in the pictures, from having a record of their abuse viewed, shared or traded again and again. They can protect their platform from hosting these images. They can do the right thing.

For more information about joining us and using our Hash List for good, take a look at IWF membership or submit a membership inquiry

Benefits of using the IWF Hash List for good

  • Tech companies can protect employees and customers from accidently stumbling across known child sexual abuse imagery on their platforms.
  • They can make sure staff welfare is prioritised, by shielding teams from having to view this distressing imagery.
  • Every one of the images and videos on our Hash List have been viewed and verified by expert human eyes. Companies can be sure the pictures are criminal.
  • IWF hashes cannot be reverse engineered back to the images. This means anyone handling this sensitive data is completely safe.
  • Preventing criminal imagery of children from being uploaded onto networks in the first place helps stop the cycle of abuse. It’s the right thing to do.

Why should companies join our Hash List rollout?

Sadly, if people can upload, download, view or host images and videos on a tech platform or service, then it could be abused by criminals. But, it’s also true that the Hash List could be used to protect that service from inadvertently hosting child sexual abuse imagery.

The Hash List can work in a preventative way. It can stop the abuse of legitimate websites, services or platforms by child sexual abuse perpetrators. It makes networks safer for customers and employees. It protects victims of child sexual abuse from the trauma of having a record of their abuse circulated online. It gives them peace of mind.

How does it work?

Every criminal image we assess is hashed by an experienced analyst. This covers the two formats we provide the List in: Microsoft’s PhotoDNA; and a more traditional, MD5.

Licenced Members can download the list in two ways. Firstly, via our API, avoiding the need for additional, external hardware and making access to our list even more secure.

Secondly, we’ve teamed up with Microsoft so that companies can use PhotoDNA to access our Hash List, with a cloud-based automated system. We know it’s impossible for most companies to manually scan every image and video that’s uploaded onto their platforms. So, our Hash List does this in the background, without affecting the experience of users.

It means companies can compare anything from a single image or video, to the millions of images and videos uploaded through platforms daily. The Hash List can flag criminal images and videos already on systems and prevent new ones being uploaded. 

Enhanced quality checks

Each child sexual abuse image or video is independently assessed by two people. These enhanced quality checks mean every image, or video is categorised accurately, before it is added to the Hash List. The giants of the tech world trust our IWF Hash List and use it with legal confidence. We add thousands of new images every week.

International Deployment with IntelliGrade

With IntelliGrade, we enrich our hashes with additional contextual metadata. A key benefit of this enrichment process is that hashes generated by IntelliGrade are compatible with child sexual abuse laws and classification levels in the UK, US, Canada, Australia, New Zealand, and the Interpol Baseline standard.

This is important. It means we can provide a dataset of child sexual abuse imagery hashes that are compatible with multiple legal jurisdictions, worldwide. So, companies who provide services to single countries, or have a multi-national platform, can use our hashes.

Better than traditional hashes

We aim to help the tech community keep ahead of the criminals. Unlike traditional hashing technology, an image can be resized, cropped or colours changed and our PhotoDNA hashes will still find a match to the original image. It’s clever stuff.

How do we find criminal images and videos?

The criminal images and videos of children we hash come from:

  • Reports from ordinary people to our Hotline.
  • Our analysts hunt for criminal child sexual abuse imagery online. We are one of the only hotlines in the world doing this.
  • The UK Home Office’s Child Abuse Image Database. This includes some criminal images that haven’t appeared online, so the hashes are preventative.

Who can use it?

IWF Members can use the IWF Hash List under licence. Companies that use the list include:

  • Hosting or file-sharing services
  • Social media and chat services
  • Data centres
  • Search engines

Get in touch

To talk about using our Hash List and helping make the internet a safer place, email members@iwf.org.uk or call +44 (0)1223 20 30 30

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