Or they simply pay companies with a “support contract” in return for embedding spyware that sells out customers. Seen that first hand (private key exfiltration), resigned the same day.
Lots of comments saying we need to do something about the OSS supply chain but in my estimation the problem is much worse with closed source commercial software.
They don't have to sneak into those companies tho, they just hand over something like a national security letter and do whatever they want while making it clear to the heads of the company that anyone who talks or pushes back will rot in gitmo. Why wouldn't there be at least an equivalent to Room 641A (https://en.wikipedia.org/wiki/Room_641A) in every major US corporation that deals with massive amounts of people's sensitive data and communication?
I’d also bet that you could exploit the tiers at many companies: how many places have more robust review for the staff engineers but then assume that some lowly “ops monkey” will take care of the build environment, etc.? I’d hope that wouldn’t work at Google, Microsoft, etc. but have heard enough stories about disparities between which jobs are contracted out and which have the coveted FAANG benefits that I wouldn’t exactly be shocked if it turned out otherwise.
Example scenario: "malicious engineer in say Microsoft, finds out that office365 is using xz internally and the library is pulled directly without code review. Same engineer or another member of same group would be that Jia Tan doing the necessary backdooring in xz to target office365. And bam all worlwide Office365 accounts would be backdoored."
I am not saying Office365 is using xz, I have no idea really, but this would be a possible scenario. I know MsTeams is using ffmpeg for example.
So I think having this discussion while only scoping linux distributions is a big mistake. xz project was particularly interesting as a target as it is distributed under BSD zero-close license, which is pretty much a public domain license. You don't have the attribution part of the BSD license so there are probably myriads of proprietary software using it too without them acknowledging it.
In some cases they don't even need to introduce backdoors themselves but just review and spot bugs they don't correct or raise issues for but communicate to mothership. They could even work in team with having one building the backdoor and the other approving the code.
Most companies have more thorough processes to avoid this but that doesn't mean those processes are applied correctly everytime, especially if more than one malicious engineer is involved.