tt400 wroteSo assuming I just formatted without overwriting, the malware can't "reactive" (or undelete) itself without the use of another program (whether from USB, BIOS, downloaded etc.)? Are you sure?
There is no way malware can reactivate or undelete itself after a reboot without use of another program (itself or a helper application.
No current filesystem allows or supports doing such a thing. There is no physical way for an application to do that on its own.
Your RAM doesn't permanently store anything and neither does your graphics card's memory.
@Stygmata. Bios is a closed source piece of firmware. How can application run itself from bios or append itself to the bios to begin with? And doesn't windows kernel take over?
The same thing applies to the hard disk's firmware. The firmware is closed source. We don't know how to infect it.