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To "overwrite" in a computer term means to write new data on top of existing data, replacing it completely on a storage device. This process is often used to save a new version of a file but can make the original data irrecoverable. A common example is saving a new version of a document that has the same name as an older one, which replaces the old file entirely.

Key aspects of overwriting

Replacement: New data completely replaces the old data in the same physical space on the storage medium.

Irreversibility: The original data is typically lost and cannot be recovered unless a previous version was backed up elsewhere.

Common use cases: Saving a new version of a document or file, which replaces the previous one. Formatting a storage device, which erases all existing data to prepare it for new use. In-app typing: Some applications have a typing mode where characters typed will replace existing characters, rather than inserting new ones between them.

Secure overwriting

Sensitive data: For sensitive information, a process called secure overwriting is used to prevent unauthorized users from recovering the original data.

Method: Secure overwriting involves writing meaningless data or random patterns over the original data, as defined by NIST.

Purpose: This makes the data irretrievable even with specialized data recovery tools.