I knew about malware that can reside in the BIOS, but not the ones that reside in the RAM and can download itself from the internet each time you boot up the computer.
I make an image of my OS drive about once per month, and keep the last 2-3 images. If I ever suspect malware or have any other problems, I can restore from the image in about 15 minutes. I did have an infection some time ago that Windows Defender identified and "supposedly" removed, but it kept coming back, so the disk image came in handy - no more virus. I clicked on an email I thought was from my sister, but wasn't, so that's how the malware got in.