A method for write protection in a storage system using both the "file-level WORM function" and the "block-level WORM function". The block-level WORM function has two modes: the first mode is to prohibit both file access and block access, and the second mode is to prohibit block access only. When a user uses the file-level WORM function to prohibit write access to a file in a volume, a file access invokes the first mode of the block-level WORM function to prohibit write access to the volume where the write prohibited file resides.