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Nightshade, the free tool that ‘poisons’ AI models, is now available for artists to use
(venturebeat.com)
This is a most excellent place for technology news and articles.
Those companies don't make the technical details public and I don't follow the leaks and rumors. They almost certainly use, broadly, the same approach (latent diffusion). That is, their AIs work with a compressed version of the image to save on computing power.