Secure Deletion and Key Destruction

When you delete a file with rm or move it to the Recycle Bin, the operating system only removes the directory entry pointing to the file. The actual file data remains on the storage medium until new data overwrites those sectors. A forensic tool can recover the data by scanning for the unallocated sectors. This is why secure deletion requires more than a simple delete operation.

Older magnetic hard drives with very high-density platters can theoretically retain ghost magnetization after a single overwrite, allowing data recovery by specialized labs using magnetic force microscopy. This was more relevant to older drives; modern high-density drives make such recovery impractical due to track width and bit density. However, the concern drove multi-pass overwrite standards like DoD 5220.22-M.