USEFUL SOFTWARE | Free, Open Source, Commercial

[Mudbill]

Some of these have a good reputation, so you're pretty safe to download them. Generally, just try to avoid shady, small, too good to be true kinda software. Don't click ads or install promoted addons and try to stay away from programs that cheat systems or do illegal things, like generate keys or serials, because from what I gather, they are more likely to contain malware, if they are anything else at all to begin with.

I say you should just get some good antivirus software. If you're unsure of the download, run it through https://www.virustotal.com/ and you can also try setting up a virtual machine for sandbox testing if you expect it has a virus or are curious if it's a false positive. But generally, I don't think you need to worry about such.

If you get something that is open source, you'll most likely not get anything bad. CC-licensed programs are also usually a safe bet. And, of course, something with a certain amount of positive reputation, like GIMP, should be totally safe. The only time I see something with these criteria being malware is when you download it from a third party provider or (in the ultra rare cases) when the website has been compromised. Avoid websites like softpedia and those with download managers and bloatware to the rims. Always check to see if you can get the software from the original website.

There you go, you should be totally safe.