Hi, suppose a PC is infected with (unknown or Darkcomet) RAT by crooked X, then afterwards Cunning Z comes unknowing that it's already infected by X, infects/or at least tries to infect it. So now what would happen? Would X RAT prevents further infection? Or Both RAT's have access to device? Or would X lose his access since Z overthrew X, infected with his own RAT on top? Or if both coexist Would both X & Z able to see conflicting each other's RAT presence, see each other RAT's vicious activities (or even further trying to fight to remove each other from device) ? Or even see address of each other's C&C server?
It would all depend how your machine is secured on one hand and on the other hand, what kind of apps are used by the RAT's. Many (countless) scenarios are possible! Important for to avoid such, is the security stage of both, your computer and your internet connection via Modem/Router.
That would depend on which port was being used by either RAT for remote com, and whether either RAT was competing to be in the boot sector. As far as the boot sector goes, it's last one in is the winner. And then it depends on how the RAT code was written with regards to persistence, and what it does to remain in the boot sector.