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The best summation I've viewed on what exactly are Zip files.

I think it's a good idea to have an old laptop with nothing on it to test any files on that you're worried about.

Three items: 1) Opening a zip file is safe, even if it contains malware. If you open the zip file, and run the enclosed malware, then you are in trouble. If, for example, a zip file contains a photo (a jpg file). If you never click on that jpg file to open it (to view it); if you just let that jpg file sit there, then it is basically a dormant file that will never see the light of day. The same is true of an exe file that is malware. You can have it on your computer. As long as you do not double-click it to run it, it will sit there for all eternity, doing nothing. Of course, that is risky, because one day someone might be curious and double-click it. So it is best to not have it. But if you ignore it, it will sit there doing nothing, just like any other files that you have that you never touch. Opening a zip file only extracts the contents of that zip file. You can upload the exe file (or any file) to virustotal. That will give you a good idea on whether or not the file contains malware. It is not 100% reliable. But if virustotal lights up with dozens of warnings, then that is a warning that you should heed. If virustotal deems it safe, it probably is, but the key word is "probably". 2) If something went amiss with any of the files within the zip file, you will know when you try to unzip (extract) the file(s). When unzipping a zip file, the unzipping program checks the veracity of any file that you extract from the zip file. If a single byte is missing or has changed, you will see an error while trying to unzip it. So if someone wants to e-mail you a file where you must be 100% sure that nothing happened to it between the sender and you, then have them zip that file. If you unzip it, with no warnings, then you are good to go. 3) Zipping files does add compression by default. But compression is optional. You can zip files with zero compression, light compression, heavy compression, or medium compression. The benefit of zero compression is if the files you are going to zip are already highly compressed, then the zipping program will not waste time trying to compress files that it can't compress any further. But you must tell your zipping program to not use compression. For example, flac files (music files) are already compressed. You might be able to compress them a bit more. But the space you will save will be almost meaningless, and it will take much longer to complete the zipping job if you try to compress those already compressed files. This really only matters when you are zipping gigabytes of data with any modern computer. If you are zipping a few megabytes, it will be so fast that the compression time will fly by. Note that the compression is lossless. When you unzip the files (when you extract the files from the zip file), they will return to exactly what they were.

@ionu4535

4 күн бұрын

I think you should be on Leo's team; Leo?

If we are aware of the different types of files (defined by their extension) is absolutely safe to unzip a zip file and examine its content. It's obvious that we don't run any executable or script inside the zip file, if the source is unknown. Something VERY IMPORTANT to always do is to ask our file explorer to show the extension of files.

@davinp

7 күн бұрын

yes. I don't know why extensions are turned off by default in Windows. They should be turned on. If we don't know about that ZIP, we shouldn't open the files in the ZIP file

I don't think I've ever received a legitimate password protected zip file. Be extra suspicious of any of those.

Zip files in disguise: .docx, .xlsx, .exe. Zip files can be turned into self-extracting zip files(!), with the decompression code built in. And they can be set to automatically run a file that was in the archive (great for setup programs).

When using a zip program to open a .docx file, you'll see the images as separate files. Making it easy to extract those.

@davidhamm5626

6 күн бұрын

I will try that, thanks,

Good advice.. You can't.. attach any (Batch.bat Files in Email's either) unless ZIP'ed.. (I always manually scan a ZIP File) Using Microsoft Defender 👍

When I go to open any new files I right-click which brings up a list that reads "open with"... That way if malware has been maliciously mis-named as .jpg and I see that the suggested program to open it is something other than offering some type of a picture viewer I know something is up.

"The answer is, of course, it depends." I love that answer. LMFAO! Just like with everything else you do, watch out. You never know if what you've got is a zip bomb or encrypted zipped malware. :P

Hey Leo,grewt video!. Here is a ideaow about a video on Virtualization ? This zip video made me thinking how i generally check unknow zip files in windows sandbox. But is virtualization really a full proof solution? How about the malware infecting other devices that could be connected to my local network 🤔?

Thanks Leo

You just have to watch out of zip bombs.

Thank you for your many posts always worth watching. If I scan s zip file with, let's say Bitdefender, would that help?

@askleonotenboom

7 күн бұрын

I don't know. You'll have to ask BitDefender if they look inside. AND, as the video points out, even if they do if the zip is password protected they'll not be able to see its contents.

@andyh4069

7 күн бұрын

@@askleonotenboom Thanks for your reply. (sorry about the s instesd of z)

Can't I always safely open a zip file and look at the contained files as long as I don't open an exe file?

@Jan12700

7 күн бұрын

Some Viruses use exploits where just by looking at them they can be loaded and your OS be infected.

👍 nice

Zip files aren't inherently dangerous*. It's what's in them that can be dangerous. *Unless it is a zip bomb: It contains a file with simple data that can be compressed at a _high_ ratio, e.g. the file contains all zeros. When decompressed, it is far too large for the amount of space on your computer. 💣 😮