There have been quite a few similar

Watermarking has referred to this "spy" use case for quite some time. Digital items purchased for download often have them, for example. Even before the rise of digital downloads, screeners for movies had them.

if it is specifically about pictures then wouldn't an analog copy clean it up? What about adding new spymark on top of it?

If it is text, copying text alone and not the file will it not remove it? Massage the text with Ai and vola spymark gone, don't you think?

I'm not convinced spymark is better than just "invisible watermarks", spymark to my ears sounds designed to be sound very negative when invisible watermarks are not always negative, e.g. the counterfeit bank note example.

Tech like SynthID I see a net positive especially since it doesn't degrade text quality. I dream about a browser extension running at all times that makes text more translucent based on the confidence of LLM writing[0].

This article's suggestion of using it to unmask whistleblowers is very interesting and not something I'd thought about though. Still not convinced that spymark is a better name though.

[0]: Sean Goedecke's Deckard is close but it would rather invisible than bright red https://www.seangoedecke.com/deckard/

Weirdly the article doesn’t mention steganography. Arguably it isn’t quite the same, because the aim of steganography isn’t necessarily to add an identification, but something like “steganomark” would seem to be fitting.