Honestly,it would be really easy,if you are infected by a RAT/Backdoor.
Even if they know your IP,they can't "hack" your system,but they can "flood" your internet connection,using multiple shells.They may be able to turn off/restart your computer whenever they want to,using windows shutdowner.Typically it's hard to do it from long distance,but they can use "Zombie computers" to do it,only if they are near your location.
Why would they "hack" your system,it takes a great deal of time and effort.