I'm trying to learn more about computers and often I have to download a file. I find what I consider is a trusted site- for example maybe someone mentioned it on a udemy course I'm taking. So often, I download the zip or exe and windows defender pops up and scares me, saying something like 'opening these files may be harmful to your computer'? For example this just happened when I tried to download the quick hash program (of all things).
Ok so it always does make me worry a little bit because I don't want to get malware on my pc, but my question is what is it's criteria or basis for flagging some files as suspicious? I have avoided downloading certain files I think are safe, because of this. Is it because these files lack a certificate or digital signature or something? How do I know when it's ok to install or download? Thanks!