People still manage to write exploits today, but now you must find an ASLR leak, you must chain enough primitives to work around multiple layers of protection, it's generally a huge pain to write exploits compared to the 90s.
Today the dynamic detection that we have for Linux packages seems thin to non-existent, like the arms race has not even started yet. I think there is a bit of low-hanging fruit to make attacker lives harder (and some much higher-hanging fruit that would be a real headache).
Luckily there is an asymmetry in favor of the defenders (for once). If we create a scanner, we do not _have_ to publish every type of scan it knows how to do. Much like companies fighting spammers and fraud don't detail exactly how they catch bad actors. (Or, for another example, I know the Tor project has a similar asymmetry to detect bad relays. They collaborate on their relay scanner internally, but no one externally knows all the details.)
Indeed, defenders are often outgunned, but at a minimum we’ve pushed the level of effort way into nation-state territory, which is a good start.
If the prior is 1 was out there (this one), the chances that there is 1+ still undetected seems fairly high to me.
To behaviourally detect this requires many independent actors to be looking in independent ways(e.g. security researchers, internal teams). Edit: I mean with private code & tests (not open source, nor purchasable antivirus). It's not easy to donate to Google Zero. Some of the best funded and most skilled teams seem to be antivirus vendors (and high value person protection). I hate the antivirus industry yet I've been helped by it (the anti-tragedy of the commons).
Commonly public detection code (e.g. open source) is likely to be defeated by attackers with a lot of resources.
Hard to protect ourselves against countries where the individuals are safe from prosecution. Even nefarious means like assasination likely only work against individuals and not teams.
That would surprise me greatly
I want to name one thing: when Windows failed to load a DLL because a dependency was missing, it doesn't tell you what was missed. To get the information, you have to interact with the DLL loader with low level Windows APIs. In some circumstances Linux apps may also have the need. Like for printing a user friendly error message or recovery from a non-fatal error. For example, the patchelf tool that is used for building portable python packages.
> No one wants a Linux antivirus
It is not true. Actually these software are very popular in enterprise settings.
ClamAV has been around for a very long time at this point.
It's just not installed on servers, usually
A cloud provider can take snapshots of running VMs then run antivirus scan offline to minimize the impact to the customers.
Similarly, many applications are containerized and the containers are stateless, we can scan the docker images instead. This approach has been quite mature.
Why "new uploads" and not also "all existing"?
Games and proprietary software will sometimes ship with DRM protection layers that do insane things in the name of obfuscation, making it hard to distinguish from malware.
But (with only a couple exceptions) there's no reason for a binary or library in a Debian package to ever try to write the PLT outside of the normal mechanism, to try to overwrite symbols in other modules, to add LD audit hooks on startup, to try to resolve things manually by walking ELF structures, to do anti-debug tricks, or just to have any kind of obfuscation or packing that free software packaged for a distro is not supposed to have.
Some of these may be (much) more difficult to detect than others, some might not be realistic. But there are several plausible different ways a scanner could have detected something weird going on in memory during ssh startup.
No one wants a Linux antivirus. But I think everyone would benefit from throwing all the behavioral analysis we can come up with at new Debian package uploads. We're very lucky someone noticed this one, we may not have the same luck next time.