New Hackers go though walls ?

I build yesterday my House on a New Server with like 40-50 Players on it.
My house have 2 floors
The Problem is now, i came today online and check my house, but !, all my things in my house, all Chests, and furnances are cleaned without a door is opened or a wall got destroyed with c4, although in my second floor ! with now Stair on the side to go in it

And this is the Problem, the hackers cant get into my second room without a hack, my doors are all locked only on me and for the second floor they need stairs, but there isnt a stair

Sry for my bad english but for that situation i dont need that…

They planted C4 on Walls and later built them back again. Thats all.

You dont understand ?
They could come into the second floor with c4! and they had not placed any stair

You don’t need any stairs. Build a Large Wooden Storage Box and a Wood Barrikade and you are at the second floor. You can destroy them afterwards.

Make no sense, server for like 12 horus on and they have 6 c4 for my little base with only a little box in every room and not more ?