This topic seems like a pretty easy answer, but I cant figure it out. In my game, there is a timer. Once you reach the finish line, the timer script checks to see if finished (a bool value) = true. If it is, the timer stops. If its not, it keeps going. My question is where is the best place to put this bool value (StarterGUI, ReplicatedStorage, ect.) for the best security.
I’m not sure what category this should go under, tell me if I got it wrong
Have a good day! 
If you want this value to not be thwarted with, then I would suggest you not put it anywhere client related such as PlayerGui, PlayerScripts ect. I would personally put this inside the players character, however you might want it somewhere else depending on what you want to do with it. The important thing security wise is to make sure you have FilterEnabled on, and never try to access this value from the client. Otherwise a exploiter could mess with the value, and you would be taking the altered value. Always handle data on the server. Hope this helps!
Sorry, I misunderstood the question.
Edited:
I would place this bool value in the Player when they join the game using the PlayerAdded event.
No, please don’t. Putting anything inside the character you don’t want to be messed with is a bad idea in itself. Apperently, weird thing, anything in the character/changed on the character is replicated, you can change the torso size and it replicates on server. You can see this yourself by going into studio, changing the torso size on the client, then viewing on the server.
Better place would be ServerStorage or ReplicatedStorage, yes players can hack and see what value the boolvalue is, no, they cant change it in replicated storage. Server storage doesn’t let them see it at all.
Also, this should go in scripting support, fits it more imo
I completely forgot about that @3rdhoan123! Thank you for reminding me. In that case I would personally use a module script to handle the player data so it does not get too messy. I always find that having a thousand bool values hanging around in my ServerStorage can be annoying.
So all things related to game security should go in the scripting support category, and thanks for the advice!