In February 2015, IS published 892 propaganda pieces – videos, photos, audio and written articles – across their digital output. In the same month this year, that fell to 570 – a decline of 36%.
According to the International Centre for the Study of Radicalisation and Political Violence (ICSR), which provided the data, the nature of that propaganda effort has changed.
In 2015, 53% of IS’ output focused on Utopian depictions of life under the so-called caliphate, with 39% glamorising jihad.
This year, as the battle for Mosul raged, 80% focused on jihad and only 14% on Utopian imagery.
Sources in UK counter-terrorism confirm that the quantity – and quality – of IS propaganda has declined, but their focus has shifted to lone wolf attacks.
Charlie Winter, a senior research fellow at the ICSR, told Sky News: “It’s much more difficult now to stumble across Islamic State propaganda, there’s no question of that.
“But the brand is still out there. So through terrorism, through adopting attacks like that carried outside the Houses of Parliament on Wednesday, it’s actually able to use that as propaganda, it’s able to use those attacks as a way to keep itself at the forefront of people’s minds.
“And in that sense propaganda and terrorism are one and the same thing for Islamic State.”
When IS occupied Mosul in June 2014, it also took an important staging ground to spread its ideology through digital means.
It flooded open platforms like Twitter and YouTube with thousands of videos, aiming for maximum reach. A mixture of horrifying murders – including the US journalist James Foley – and soft-focus features about life under IS rules. Both were important in spreading its brand and ideology to a mass audience.
Over the last three years, though, both Twitter and Google have grown much more effective at removing IS content from their platforms.
That has forced IS into less high-profile channels, including Telegram, an encrypted messaging app where the group remains active.
Ross Frenett, co-founder of Moonshot CVE, a startup which uses technology for counter-extremism, told Sky News: “If someone is in a closed Telegram channel for IS, or Daesh, they are most likely already quite far down the path of believing in the ideology.
“Whereas previously, when they were pushing stuff out in the broader Twittersphere, the messaging was much more for a broader and wider audience.
“They are now focusing considerably more effort on weaponising vulnerability. So identifying individuals that are vulnerable from a social perspective, a mental health perspective, and trying to encourage those individuals to carry out lone wolf, single actor attacks.
:: Sky News will be showing a special programme – Terror In Westminster – at 7.30pm tonight