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Comment by daenz | Hacker News Reader

I've always wondered if jpeg encoders added something like this to screenshots. Should be possible to add a compression-resilient pattern that encodes the screenshotter's host details.

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Blizzard watermarks screenshots produced by World of Warcraft find and track users of emulated servers by embedding user account info and server IP all across the image.

https://www.ownedcore.com/forums/world-of-warcraft/world-of-...

Fascinating stuff. I didn't think my trust in software could be broken any more, yet here I am.

I assume you are aware modern games are tracking everything players do. The have heatmaps and everything. It's been going on for quite a while

I'm much less bothered by the idea of developers having access to things like aggregated anonymous heat maps, and more worried by the amount of individual details required to generate such a heat map.

I am, yes. But this was not the case when I played WoW 15 years ago. I mean, I knew that I was playing on a server, and of course they are tracking everything on a server. But for some reason this steganography in the screenshots just gets under my skin.

With current games I go in with the assumption that I'm in a public place, and act accordingly. But back then I really counted on my Personal Computer being personal, so this feels like a breach of trust.

It's not the software. It's the humans that write the code. Someone had to do it.

It would be interesting to know if there are some GDPR ramifications here. Do Blizzard leak private data if I grab a screenshot and share it publicly?

I'm not sure about jpeg, but with an algorithm like 'deflate' the encoder is constantly making decisions about whether it's more efficient to represent a series of bytes as a literal or as a reference to a previous series. I think a steganographer could take advantage of that by encoding something like a tracking number in the form of the occasional less efficient decision.

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