When a file is removed, its blocks are generally put on the free list without being zeroed out. From a security perspective, would it be a good idea to clear freed blocks? Why? If so, would it be...

 When a file is removed, its blocks are generally put on the free list without being zeroed out. From a security perspective, would it be a good idea to clear freed blocks? Why? If so, would it be better to clear the block out before it is put on the free list, or should it be zeroed out before it is used again in another file? Why? Why isn’t this typically done on file systems today?