Every once in a while security researchers would discover sophisticated exploits that would allow malwares to take over your computer via multimedia files, but those are actually rarely exploited in the wild by run off the mill malwares.

Unless you're an important person being targeted by hackers and three letter agencies, your biggest source of threat is running infected programs from untrusted sources, e.g. cracks downloaded from random torrents or warez sites, shady sites serving ads that trick you to run some executables, etc.

Definitely no, viruses need 48-72 hours of incubation before the .mkv host becomes contagious. If the file is <24 hours old, I'd look for another source.

If you're worried your computer might be infected, you should consider swapping your case LEDs with UV lights to purify your system.

someone please correct me if I’m wrong but I believe that for it to be possible, the application that plays the mkv file would have to have a remote execution exploit and the code for the virus would be executed through the player. the player would be required to have elevated privileges. I think this is exceptionally unlikely for vlc

You’re probably fine it’s extremely unlikely. Dont trust emails that say they recorded you wanking its a scam

Like someone else said, it's unlikely. However it is possible but it would need to exploit your media player (VLC) and/or your OS. As long as your source is trustworthy you shouldn't have to worry, that's why the megathread is there.

Your wife is not going to believe it bud.

Absolutely yes. Even if it is not disguised executable.

It could contain an exploit which targets the video player you are opening it with.

There's imho no stupid questions regarding personal cyber-security. There are only things we don't know yet.

theoretically… but no.

Afaik, it's possible for any file to be infected with a virus. Videos themselves can be, and .MKV is a container of other files (video, audio, subtitles). The video source, audio source or even .txt containing the subtitles could be a malicious virus inside the container.

In general media files can be formed in a way to trigger some bug in the media player, sometimes in ways that allow to overflow buffers and start ROP chaining.

About 8 years ago there was this media file going around crashing any iPhones that tried to play it with the integrated player.

Of course crashing is way easier than code execution. So overall your scenario is unlikely. VLC also does not yet know of any issues with 3.0.20: https://www.videolan.org/security/

The 3DS got rooted by playing a music file. Anything can happen homie.

Not really, but you can get a virus from movie.mkv.exe, which will probably show up in windows as "movie.mkv" but will actually run a program.

That being said, I've never actually seen this in the wild and it was mainly talked about in the mp3 era.

In theory, you could make a fake executable with the mkv file extension on a unix system, by making it a shell script with a bunch of garbage data at the end, marking it executable, and distributing it with a tarball. But the chances someone will do that is insanely low.

Also it has caveats:

1. It'd rely on your double clicking it, and having your file manager not warning you about it.
2. Video players wouldn't run the shell script code, if it'd run the file at all.

You're on linux? The odds of you getting a virus on linux are not 0 but very slim, since the userbase is very small.

Plus, viruses prey on people's ignorance. The usual "movie file viruses" are .exe files and can only be run on windows. Most people don't enable the option to show file extensions on windows, so a filed named "movie.mkv.exe" would show up as "movie.mkv" instead.

IMO, the odds of you accidentally running a virus by playing a .mkv file on linux are as high as the odds of you winning the lottery 3 times in a row.

if you really only played it and it didn't abuse some zero day in vlc (extremely unlikely), the there's basically zero chance you could have activated a virus.

Just make sure the file doesn't have a double extension. That can trick people into running a .exe when the file extension is hidden. That's really only a problem on windows though.

I'm gonna go with unlikely.

It’s possible to get a virus from any data that enters your computer full stop.

Likelyhood wise: that virus on the MKV will have to attack the operating system preview system (which means you fucked all the way up to personal nation state attention), or attack the video player (which is a lot more likelier, they discover theoretical exploits all the time).

You’re talking about streaming with VLC? Was it a trusted source? Cause otherwise the FBI or script kiddie has probably fucked you up.

Depends what you play it through TBH. If a program has access to your memory, then yes. Naturally it's a nuanced answer and unless you are a security expert that knows exactly how memory is allocated and how elevated privileges work, not to mention all the little bugs, etc. in your system, then the answer is yes. You aren't really safe from anything that hits your hard drive.