One tool is called nightshade:

https://nightshade.cs.uchicago.edu/index.html

There is a second tool but I forget the name.

[edit]

Found it; name of Glaze: https://glaze.cs.uchicago.edu/

[edit]

relevant nightshade discussion: https://news.ycombinator.com/item?id=39058428

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Unfortunately, I would assume all public works, and many private ones, on the internet have been consumed by LLM training models, and done so illegally, in my opinion. Finding out if it has been consumed is also probably impossible. You could try filing a Freedom of Information Act request (FOIA), but that is no simple matter.