WannaCry was able to successfully run on ReactOS in 2025. Most other virsuses do tend to crash, because the memory layout is just a tiny bit different, but yeah, compatibility means compatibility. Lots of malware comes along for the ride.
However, there is a permissions layer that is more nix than Windows, which means the first foothold is still better than XP - you have to choose to execute the file. Self-running things don't tend to infect systems.
Its not a panacea, and there is a risk factor. And there aren't a lot of antivirus systems that can run correctly under ReactOS, because they freak out and think the OS is the malware, because they're scanning hashes for Windows, not another system.
But for a hobby OS, keeping hardware and software accessible after the rest of the world broke access, it still works.
Of course. Maybe not successfully but a "virus" is just software. If it runs software, it runs software, full stop. Maybe the same APIs are not available or behave differently, so it may be buggy or non-functional, but that's true of Half-Life here too.
Somewhere in the docs they state that they must also recreate whatever bugs the API has, otherwise applications written with those bugs as an (implicit) assumption could misbehave.
its worse than that, Windows activates/deactivates "bugs" based on the compatibility profile of the app.
so you can set an app to use a Windows XP compatibility profile, and this will simulate Windows bugs which were fixed in more recent versions of the OS
Maybe worry about Linux malware which is a major problem right now everyone is in huge denial about, instead of throwing shade at a hobby OS emulating a 25 year old version of Windows.
ReactOS isn't the one that just had one of its package repos owned (again).
Isn't it funny how such incidents on Linux are rare enough that they make headlines, but on Windows that's been the baseline expected state of things for so long that nobody bats an eye anymore.
Btw if you're running an OS that's never had a malware incident, please, tell us!
...is essentially impossible to pull off against commercial operating systems, because their core components are all written in-house by staff with photo ID badges, details with HR, tax returns filed with the government, and a cubicle that makes sure that they're locals and not some faceless anonymous hacker identifiable by nothing other than a throwaway faked email address!
I get that there was a lot of "stigma" about open source, the world largely forgot about it, but... actually, in this sense of allowing anonymous contributions it remains a very real risk.
"Jia Tan" was almost certainly a paid professional hacker working for a nation-state actor. Their "helpful contributions" to XZ utils was nowhere near a full-time effort. They certainly had "other irons on the fire", most probably in the Linux kernel or immediately adjacent to it.
He's probably not the only one doing this kind of "work".
For all you know, Linux has more remote exploits purposefully baked into it than Windows has security bugs inadvertently left in it... and don't forget Linux has bugs leading to security vulnerabilities too!
A rough count of "named" CVE 10.0 score (or close to it) vulns in the last 5 years:
7 for Microsoft: ProxyLogon, ProxyShell, ProxyNotShell, LDAPNightmare, PrintNightmare, noPac, Follina
WannaCry was able to successfully run on ReactOS in 2025. Most other virsuses do tend to crash, because the memory layout is just a tiny bit different, but yeah, compatibility means compatibility. Lots of malware comes along for the ride.
However, there is a permissions layer that is more nix than Windows, which means the first foothold is still better than XP - you have to choose to execute the file. Self-running things don't tend to infect systems.
Its not a panacea, and there is a risk factor. And there aren't a lot of antivirus systems that can run correctly under ReactOS, because they freak out and think the OS is the malware, because they're scanning hashes for Windows, not another system.
But for a hobby OS, keeping hardware and software accessible after the rest of the world broke access, it still works.
Of course. Maybe not successfully but a "virus" is just software. If it runs software, it runs software, full stop. Maybe the same APIs are not available or behave differently, so it may be buggy or non-functional, but that's true of Half-Life here too.
Some, but not all, most don't. Ideally they would all work, ReactOS doesn't make a priority on being a "safer" option, just an open source option
Somewhere in the docs they state that they must also recreate whatever bugs the API has, otherwise applications written with those bugs as an (implicit) assumption could misbehave.
its worse than that, Windows activates/deactivates "bugs" based on the compatibility profile of the app.
so you can set an app to use a Windows XP compatibility profile, and this will simulate Windows bugs which were fixed in more recent versions of the OS
The payload yes, the exploit hopefully not.
Yes
You can run WannaCry under Wine, with a bit of effort.
Maybe worry about Linux malware which is a major problem right now everyone is in huge denial about, instead of throwing shade at a hobby OS emulating a 25 year old version of Windows.
ReactOS isn't the one that just had one of its package repos owned (again).
What's the major Linux malware problem that everyone is ignoring
AUR got hit recently [0], by what looks like more work of TeamPCP and friends.
EDIT: Worth noting, Arch ain't hosted on AUR. That's the community side only.
[0] https://archlinux.org/news/active-aur-malicious-packages-inc...
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Isn't it funny how such incidents on Linux are rare enough that they make headlines, but on Windows that's been the baseline expected state of things for so long that nobody bats an eye anymore.
Btw if you're running an OS that's never had a malware incident, please, tell us!
Does Genode or Sculpt count? :)
https://genode.org
Conversely, this kind of attack: https://en.wikipedia.org/wiki/XZ_Utils_backdoor
...is essentially impossible to pull off against commercial operating systems, because their core components are all written in-house by staff with photo ID badges, details with HR, tax returns filed with the government, and a cubicle that makes sure that they're locals and not some faceless anonymous hacker identifiable by nothing other than a throwaway faked email address!
I get that there was a lot of "stigma" about open source, the world largely forgot about it, but... actually, in this sense of allowing anonymous contributions it remains a very real risk.
"Jia Tan" was almost certainly a paid professional hacker working for a nation-state actor. Their "helpful contributions" to XZ utils was nowhere near a full-time effort. They certainly had "other irons on the fire", most probably in the Linux kernel or immediately adjacent to it.
He's probably not the only one doing this kind of "work".
For all you know, Linux has more remote exploits purposefully baked into it than Windows has security bugs inadvertently left in it... and don't forget Linux has bugs leading to security vulnerabilities too!
A rough count of "named" CVE 10.0 score (or close to it) vulns in the last 5 years:
7 for Microsoft: ProxyLogon, ProxyShell, ProxyNotShell, LDAPNightmare, PrintNightmare, noPac, Follina
10 for Linux: XZ Utils, regreSSHion, Leaky Vessels, Copy Fail, PwnKit, Dirty Pipe, Looney Tunables, GameOver(lay), Baron Samedit, Sequoia
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Windows stopped having serious malware problems at least 10 years ago
the ransomware campaigns would have happened on any OS enterprises use, because they were not security flaws in the OS
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