[flukus]

> Filesystem permissions cannot be controlled on a per app level

They can if you adopt a user per app model. I thought this is what android/UWP did under the hood.

> I do not like the fact, that an installation of for example a game needs admin rights, and has every chance to access data it should not be able to do.

I doesn't. The biggest cause of this is the default of requiring admin to access program files, even if it's only touching it's own new folder.

Installing off steam happens without admin rights, apart from the VC++ redistributable (why is that a thing?).

[WorldMaker]

Steam is a terrible security example because Steam just gives Everyone Read/Write/Execute access to its folder(s) on Windows. The Steam solution to permissions on Windows has always been to basically just give up and not bother.

[flukus]

Has it ever been a problem in practice? I'm not aware of it ever being one. Worst case scenario some malicious software destroys a game install and some saves, unpleasant but not the end of the world.

It comes with some great benefits though, like easy modding. Imagine if my text editor couldn't access my games folder?

[WorldMaker]

Every day I'm surprised there hasn't been some malware that strikes at the default Steam install locations. The malware would not need admin access, could easily just wipe out the whole directory and be a noxious pest. More concerning, with a bit more work malware could trojan every EXE and/or DLL in the directory and likely won't get caught [1]. Once trojaned, all that any of the EXEs need to do is pop up a decent mockup of Steam's "Installing VC Redistributable" dialog [2] and get an easy UAC prompt opportunity (that Steam has already taught most gamers to expect semi-regularly) and from there full admin rights...

Not that I want to give malware devs any ideas, but I would be surprised if the above never crosses their minds. I suspect the main reason that it hasn't happened to date is that most malware devs are likely gamers and don't want to defecate where they eat.

As for the "great benefits", as much as I like modding, I like my system security a little bit better. There are definitely ways to do modding both securely and easily (and reproducibly) using things kind of like Docker containers and patch overlays, and I'd love it if, say, Valve invested some time into that as a secure platform service. For some of the games it supports Steam Workshop gets sort of, partly there, some of the time...

(But ultimately, I think game developers mostly don't care about security and Steam especially isn't very well incentivized to move out of the dark ages anytime soon. Bringing things back around, I'm hopeful that with the UWP platform exploring things like modding as a service we'll at least see that sort of innovation from Microsoft and the UWP converge towards the best of all worlds, eventually, hopefully...)

[1] Steam has a baroque assortment of DRM and anti-cheat mechanisms, obviously, but only while it is running and even then most of them are passive when a game isn't running. Steam absolutely has no idea what would be legitimate modding to game EXEs (as many mods do that) and what would be trojan-ing. Most people leave Steam running just about all the time, which locks down some of Steam itself, but not everyone does and all it takes is finding one good crash vector for Steam...

[2] Steam also seems to be several anti-practices here because as far as I can tell Steam doesn't ever bother to check if VC Redistributables or DirectX are already up to date on the system, it just spams the installers regardless...

[emodendroket]

Well, I mean, if I'm picking, I'd rather other applications can get to my games folder than the other way around.