But it seems like this is roughly in keeping with the level of trust you need to give an anti-cheat program for any kind of cheat scans. Nothing seems materially different about DNS versus file handles versus memory.
I'm pretty sure that you can't figure out open file handles for anything but your own process in Windows, unless that process has administrator rights.
The same should be true for memory contents. Which means VAC could check the game's own process memory, but only get names of other processes running under the current user - w/o memory contents of those processes.
Which means VAC could check memory and open file handles of the game, that is running, but nothing else. Which is fine in my book.
The DNS cache however is different. It's shared between all applications running on your system.
Looking at the process list, they could figure out that I'm currently running firefox - but nothing more. By looking at the DNS cache, they can figure out which sites I visited including my e-mail provider and much more. For example software that checked for updates and so on.
You could just extend your argument further and allow them to go through cheater's browser history, because "they are just looking, if the targeted user visited cheat websites". There is anti-virus software, that is monitoring visited websites to protect the user, so quite similar. Normally such anti-virus software doesn't send the visited websites back to the anti-virus company. And if they did, it would be a privacy violation as well.
“VAC checked for the presence of these cheats. If they were detected VAC then checked to see which cheat DRM server was being contacted. This second check was done by looking for a partial match to those (non-web) cheat DRM servers in the DNS cache
I would have liked a more specific explanation. "If they were detected, VAC then checked to see which cheat DRM server was being contacted." - so is the DNS cache read for all users and the search is only done for those users. Or is the DNS cache read only for those specific users?
I also would have expected more of Gaben. Conspiracy theories "VAC is so good and effective that hackers will desperately try to attack people’s trust ", playing the whole issue down "what porn sites you visit" and also vilifying people, that don't like this specific behaviour of their software as cheaters / cheat creators. No Gaben, I'm not a cheater and I'm also not a cheat creator. I love you, but I also love my privacy and I just don't like software, that is snooping around in my DNS cache. And that's not because of porn sites, but actually EVERYTHING else. I would have prefered a "we possibly went overboard with VAC and didn't see privacy issues, we removed that code from it". Thank you very much.
decompiling the code to poke around if not
For normal win32 programs, decompiling is quite impossible. I guess you meant using a disassembler. And that's really complicated work, especially for larger programs and takes ages to do.
Sure, one could create code, that injects itself into VAC and look around that way. But this may cause VAC to think, that the injected code is a cheat and ban you.
sniffing using Wireshark to check for data transmission
That only helps for unencryted data. For encrypted data you just know that it's transmitting something. And in Valve's case their software is supposed to communicate with their servers and the game's servers. That's expected. And I bet that the communication is encrypted, which means Wireshark wouldn't help at all.
How do you know your browser isn't currently submitting your data everywhere?
I actually figured out that Firefox is sending out data to google right when starting it. I searched around a bit and found out that it's a "feature". I don't like software, that is connecting to google without my approval especially after the NSA leaks, so I switched that specific feature off.
As a result, most people trust.
Exactly. It's literally impossible to make absolutely sure, that there is no software on your computer is spying on you and sending sensitive data out. Plenty of software does auto-updates. Firefox plugins are auto-updated every now and then, which means you would have to monitor everything constantly to make sure. But that simply doesn't excuse any software in that regard.