Like with most things it's not as simple as it looks from the outside. Malware payloads need to exist undetected by whatever system they've been deployed to which by itself is an ever changing cat and mouse game that requires a different knowledge set than simply gaining access to said system.
If you have a second computer you're willing to accidentally mess up and require a wipe + reinstall, I recommend you experiment a bit and try writing your own malware or playing with some open source variations floating around. It can teach a lot to see from the attacker's perspective.
If you have a second computer you're willing to accidentally mess up and require a wipe + reinstall, I recommend you experiment a bit and try writing your own malware or playing with some open source variations floating around. It can teach a lot to see from the attacker's perspective.