While I have never been attacked by serious trojan horses and viruses, my computer was infected with spyware when I downloaded some sketchy Chinese software that was free (I forgot what it was for, but the fact that it could do what I needed made it attractive enough for me to download it). It then hijacked many things in my computer. For example, changing the homepage in my browser and installing unknown extensions, showing pop-up ads all the time, and significantly slowing the start-up time. It also ran in the background and suspiciously took up storage and internet usage. It was such a hassle for me to get rid of it, because the attacker designed it such that it is very difficult for a clean uninstallation. I had to look through many tutorials online just to get rid of every residual file and reverse the damage. To prevent something like this from happening again, I think it is important to only download and install softwares from reputable sources. Don’t download softwares that you don’t trust simply because of convenience. Alternatively, there is also the sandbox function in Windows 10, which allows users to try running an executable file in a virtual machine environment. This enables you to test whether a software is safe or not before running in on your real computer.