What Kinds of Files Can Be Viruses?

Corrections & Notes: • The JS file is actually JScript, not Javascript

Making file extension hidden by default is one of the worst mistakes MS did.

I want to add a fact in your point that "sometimes hackers may hide the malicious files so that you can't see them by default." Even after you enable the "Show hidden files" option, sometimes they may hide it as a system file (by setting the -h and -s attribute to it). So if you're skeptical about such an item, make sure to enable the "Show hidden operating system files" as well.

The fact that "Hide File Extensions" is SILL on by default baffles me.

Fun fact, in older versions of Windows the .msp files were used by Microsoft Paint.

I absolutely don't understand why file extentions aren't shown by default in windows. It's not annoying and soooo important and also useful (for example if you have two files of different type (like a word document and a pdf export of it) with the same name and have to find the right one by icon)

Also worth mentioning, file extensions are just labels, and they can be manipulated at will regardless of the underlying data. So you might run a .cmd file or something, but the rest of the payload may be contained in a file with extension .docx exactly like a normal document, when really it's just a .dll with the extension changed.

He may not be a OneDrive synced file, but never fails to upload 💯

You also have ".jar" which is an executable java application. It's basically an executable version of a zip file, where java classes are stored within. Any code that is inside a ".jar" file will be executed and ran when you execute it.

I just love how ThioJoe makes the highest quality tech content on the platform He doesn't resort to clickbait or becoming a Linus clone He has his own style and I literally can't find anyone who makes similar content and at the same level of quality Keep up the good work

Also, docx, xlsx, pptx, etc are actually encoded as zip files. If you change the extension to zip you can see the bundle of files. This can be exploited, unknown office files should be opened in zip explorers before office.

I think the main thing or key from this is don't download things willy-nilly over the internet, use extreme caution with links in email, texting, IM's etc. Always exercise caution with attachments. Only go to reputable trustworthy sources with a careful eye. As much as I like open sources that's where you really have to be careful because of too many hands accessing the source code. But that does not mean that someone can't still attach or inject a malicious code to a paid licensed version either. Buyer/ end user beware! You are your own first line of defense, watch dog and security. Pay attention to everything, because you really have to. All the more reason to have backups should one slip past you, in hopes that you can recover. Thanks for the video Theo.

I work in the antimalware industry! More common than changing file extensions or default programs for opening files, we edit local machine group policy to prevent execution on specific file types within a folder that we dedicate to malware. Also, to preserve file names to the extent possible (and to prevent execution and changing default program associations), we just add underscores to file extensions (.exe_, .js_, .scr_). I understand that given the sponsor you wouldn’t show how to edit defender settings, but you could have gone over how to use bitdefender to better protect yourself. Antiviruses have similar settings.

You know it will be a good day when ThioJoe uploads.

Thanks for having captions, sometimes i have to watch without audio like if my bluetooth headphones run out of battery, helps alot!

Basicly all files

ThioJoe I really appreciate you adding subtitles to your videos, they are very useful

You shouldn't ever fully trust any file type really. If your picture viewer has a vulnerability, a hacker can take advantage of it by embedding malicious code to something like a JPEG. Video files, image files, sound files, game data files (it's not too uncommon for cracked games to have functions in them that allow them to load external files from the game directory and those are the real malware). Even text files aren't universally safe because theoretically a text editor (or its part, like a syntax highlighting library) can be susceptible to some kind of code injection.

Something I was literally wondering about only a couple hours back when downloading an MP3 like the old days. Great timing!

Sometimes it does take one slip up. If you ever run a file that closes and doesn't seem to do anything there is a chance that depending on where it came from it may steal passwords and other things and send them to some random person who you most likely never met or knew existed.