Question Why did TF2 suddenly tell me VAC was being blocked?

[Fastfishy2]

I was in the middle of a game of MvM, on a pretty fresh windows install (moved windows to my NVME) and suddenly got booted because "something on my PC is blocking VAC" and couldn't connect to any servers after that. Restarted the PC, verified game files, nothing. Reinstalled Steam - bingo. No more problems. I barely even had any other programs running, let alone anything that could interfere with VAC, it was just background windows processes and stuff. Hell, I even managed to catch Asus' Armory crate BS and tell it not to install this time, so that wasn't even running.

I mean, everything works fine now, but I'm just mystified as to why it would suddenly happen with no apparent cause. I think I vaguely remember this happened to me once before on a laptop, but this was years ago. And, again, I don't run any kind of mods or UI or any of that 'Quality of life' stuff that people keep talking about - the stock Steam interface and UI have always been perfectly fine to me.

Windows Defender is the only AV I have running, and I didn't see any prompts come up asking me to allow TF2 (hl2.exe) through the firewall.

 

[Ralston18]

"VAC" being Value Anti-Cheat?

If it only happened (for all practical purposes) just this one recent time then likely just an unfortunate glitch.

My suggestion is to use Task Manager, Resource Monitor, and Process Explorer (Microsoft, free) to take a close look at everything that is running on your PC.

Both when not gaming and when gaming.

Look for anything is not identifiable or otherwise you would not expect to be running. Investigate further if necessary if you find anything suspicious.

Also take some screenshots for future reference.

Then if the problem reoccurs you can take another look with the screenshots in hand for comparison purposes.

You can also look in Reliability History/Monitor and Event Viewer. Either one or both tools may have captured some error code, warning, or even an informational event just before or at the time you were booted.

Something may have launched in the background and "Steam/MvM" was not happy about that.

 

[Fastfishy2]

"VAC" being Value Anti-Cheat?

If it only happened (for all practical purposes) just this one recent time then likely just an unfortunate glitch.

My suggestion is to use Task Manager, Resource Monitor, and Process Explorer (Microsoft, free) to take a close look at everything that is running on your PC.

Both when not gaming and when gaming.

Look for anything is not identifiable or otherwise you would not expect to be running. Investigate further if necessary if you find anything suspicious.

Also take some screenshots for future reference.

Then if the problem reoccurs you can take another look with the screenshots in hand for comparison purposes.

You can also look in Reliability History/Monitor and Event Viewer. Either one or both tools may have captured some error code, warning, or even an informational event just before or at the time you were booted.

Something may have launched in the background and "Steam/MvM" was not happy about that.

Yep valve anti cheat. Nothing suspicious was running in the background when I checked task manager and system resource usage was normal. Nothing of note when it came to event viewer.

 

[Ralston18]

Gremlins....

Make some notes and (as always) be sure that all important data is backed up at least 2 x to locations away from the PC in question.

Verify that the data is recoverable and readable.

Just in case.

 

[Fastfishy2]

Gremlins....

Make some notes and (as always) be sure that all important data is backed up at least 2 x to locations away from the PC in question.

Verify that the data is recoverable and readable.

Just in case.

It was space aliens, man...

I don't have any important data to back up as it's a gaming rig only really, steam keeps a bunch of saves on cloud anyway. Full scan with windows defender was fine too, for what that's worth.