Thousands of videos, graphics and other images have been collected together to form a growing propaganda archive
One of the largest collections of online material belonging to the group calling itself Islamic State has been discovered by researchers at the Institute of Strategic Dialogue (ISD).
The digital library contains more than 90,000 items and has an estimated 10,000 unique visitors a month.
Experts say it provides a way to continually replenish extremist content on the net.
But taking it down is difficult because the data is not stored in one place.
And despite counter-terrorism authorities in Britain and the US having been alerted to this growing repository, it continues to grow.
The discovery came after the death of the prominent IS leader Abu Bakr al-Baghdadi, in October 2019.
At the time, many social media posts supporting the organisation contained a short link.
It led researchers to documents and videos in nine different languages.
They included details of attacks, including those on Manchester Arena on 22 May 2017, in London on 7 July 2005 and in the US on 11 September 2001.
There’s everything you need to know to plan and carry out an attack, said ISD deputy director Moustafa Ayad, who discovered the archive.
Things that teach you how to be a better terrorist essentially.
The ISD named the library the Caliphate Cache.
For months the institute’s researchers have studied how it evolves, how it is being administered and who is visiting it.
The data is spread across a decentralised system, rather than a single computer server.
Anyone can share the content across the web, via servers based at multiple locations.
And this hampers any effort to take it offline.
But as long as the Caliphate Cache remains live, it aids IS by providing a means to continuously seed out content.
The material is added to social-media comments pages and spread via bot accounts.
Another technique has been to target Twitter accounts linked to celebrities and athletes.
For example, IS hijacked an account belonging to a fan of the pop singer Justin Bieber and used it to promote material from the cache.