osprotect

local PF = "OS/" -- full path of file. make this file startup file
local old_fsOpen = _G["fs"]["open"]

_G["fs"]["open"] = function (path, mode)
        mode = string.lower (mode)

-- copy below 3 lines to add new files.

        if shell.resolveProgram (path) == shell.resolveProgram (PF..".lock") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF..".oslock") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF..".computer") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF.."run") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF.."createfile") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF.."notepad") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF..".search") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF.."noteread") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF..".password") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF..".osprotect") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram (PF.."editor") and  (mode == "w" or mode == "wb") then
                return nil
        end
        if shell.resolveProgram (path) == shell.resolveProgram ("startup") and  (mode == "w" or mode == "wb") then
                return nil
        end
        return old_fsOpen (path, mode)
end