I was studying about OS and ways to secure your own, I got a question which was confusing me for quite a while. I read that rootkits or certain types of malwares can gain higher access on your computer and can remain hidden for long periods of time without being noticed even by scanners and anti-virus programs. They might potentially spy on your system(more like hacker activity?).
So, let’s say the infected host is able to figure out that something is wrong and decides to re-install the whole OS (I don’t remember any specific term for this process, sorry for unprofessional language :P). But he has some very important files on his system. He decides to take backup of some of his files on google drive/dropbox, etc. Hopefully on re-installing OS again, the malwares are removed from the system. However, now that he has to recover his backup files, he downloads them on his system back again.
By any chance can this happen that the backup files were infected and contained some code/script that might run on the system again causing the malware to infect the system again?