But you don't have a service uploading it along with the URLs you visit, which is the creepy part. The ID itself can be useful for your own administration. And if such a service were to appear, it could easily be removed. Everything in Linux is optional, especially as long as you stick to open source.
How do we know? Does anyone check for things like this?
Many, many apps read /etc/machine-id if you do a quick github search.
Apps may have been silently correlating our activity for years without us knowing.
We know DHCP, EFI, GNOME, popularity-contest and many other apps already use it. There are countless ways it could be used already that are hard to detect.
Basically all source is open. Eyes are plenty. Somebody would raise a stink. People can also notice things while monitoring their network via a number of tools like Wireshark, etc. All it takes is one person to notice and share their findings.
It also helps that "Linux" isn't a monolith. One person's installation can be very different from another in terms of the software used. If one piece of software collects, that collection isn't as valuable as Microsoft's because the userbase is much smaller.
It's not perfect, but it's a hell of a lot better. A lot more resistant to abuse. Security in a lot of contexts tends to be relative like that. One's house isn't impenetrable; it's just better than another, in part because the neighborhood is better.
By way of bugs (unintended effects in code), who knows how it compares to proprietary codebases. Those also depend on the particular companies.
However, by way of intentional code that goes against the interests of the user, which would be considered security issues with FOSS but not with proprietary codebases where the interests of the company come first, things should be better with FOSS.
The latter should also be more noticeable than the former. It's possible some of the former may not have run at all, neither accidentally nor intentionally. A bug can just stay dormant without ever surfacing in practice. The latter is there to be used.
The benefit of FOSS with respect to eyes is that those eyes are better aligned with the interests of users (since it's the users looking) than the eyes on closed-source code.
It should be noted that the "correct" usage of /etc/machine-id is that you use it in a way that doesn't allow cross-correlation between different applications by using a HMAC of the machine-id with an application-specific UUID instead of using it directly. systemd-id128 has a command line flag to do this for you.
Whether everyone does that correctly, that's a different question. On the other hand, while developers should be more careful about how they use identifiers like this, if an application on your machine wants to track you they don't need /etc/machine-id.
Mobile's came at the cost of composability between programs and the imposition of policy, which are against the Unix Philosophy. I wouldn't make that trade. Mobile's a sad state of affairs, inferior to desktop in many ways.
You can most likely get better security than mobile's, you just need to e.g. learn to write your own SELinux policies, etc. Facilities are there; they just have a learning curve.
How do you write SELinux policies to allow reading only certain files in /proc, where process IDs are not known ahead? I ended up writing my own FUSE-based /proc emulation. The facilities are there, but it feels like writing your own OS.
It's hard to do a 1-to-1 comparison but if the telemetry also used a masked form of the machine-id with an application ID unique for the telemetry service then you wouldn't be able to correlate them directly.
To be clear, I think this whole story stinks but the issue here is not that OS installations have unique identifiers (machines have lots of unique identifiers -- hardware MAC addresses, peripheral composition and device IDs, screen resolution) -- it's that Windows has an auto-enabled spyware^Wtelemetry system that shares enough data for them to be able to provide that kind of data to law enforcement. This would be a privacy nightmare even in the absence of a unique OS installation identifier. Heck, they could even take regular screenshots of your screen but that would be too obvious[1].
Indeed. One can regenerate it on each shutdown / reboot. The process is a little different depending on whether one has systemd or not. It's a dbus thing but systemd ingests it and there is a specific process around updating that in systemd.
There is also the NetworkID in Firefox about:networking#networkid
Another trackable piece of information on most systems is the creation time of / which just about any application can query unless it is properly isolated. This can be turned into a short unique hash. There are hacky ways to change the Birth time on unmounted filesystems using debugfs which may result in corruption. Some overlay filesystems do not support Birth time but that is not going to help most people unless the general populous expect all applications to be isolated in name spaces and overlay filesystems but this would have to be an expected pattern across all applications universally.
stat / | grep irth
Birth: 2023-04-17 20:27:01.000000000 +0000
stat / | grep irth | md5sum
8b5e849954373f8f3c2a625847e4e858
The trick is to combine it all, which is what MS is doing. For example your MS account stores any GDIDs that you've logged in with.
If you use a different identifier to track changes in a GDID/machine-id/etc., that means you can continue tracking using mainly just the new machine-id, but you should always keep trying to correlate it with other things in case it changes.