So, I had a rootkit a while ago

[unplanned bacon]

Avast reported a rootkit almost two years ago now. It got rid of it fairly quick. Since then I think my OS has been reinstalled (C drive formatted beforehand), updates have happened and Windows 10 overwrote 8.1 (and then updated as it does). The board that was in the computer at the time that rootkit was reported is no longer in use.

I watched a video on what rootkits were and started thinking, could it still be hiding in the system somewhere? There's nothing to suggest my PC has anything wrong with it though

 

[thx1138v2]

There have been a couple of viruses described lately that left code in the BIOS so even if you installed a new boot drive the code would still be there. It seems highly unlikely that you would have a problem and not noticed it because of the sequence of updates you've done but I guess it's possible.

old bios <-> old boot drive
replace boot drive
old bios -> new boot drive
old bios <-> new boot drive
replace OS
old bios -> new boot drive
old bios <-> new boot drive
replace mobo
new bios <- new boot drive
new bios <-> new boot drive

On the other hand, if you don't have any indications of a problem don't worry about it other than just doing your normal scans and protection. If that particular root kit that you encountered didn't have BIOS infecting code you don't have anything to worry about.

 

[unplanned bacon]

I checked with Malwarebytes' tool and it was clean. I changed board since that first infection though