Write protection

IBM tape reel with white write ring in place, and an extra yellow ring.
From top to bottom: an unprotected Type I cassette, an unprotected Type II, an unprotected Type IV, and a protected Type IV.
A sheet of 5-1/4" floppy disk write protect tabs.

Write protection is any physical mechanism that prevents modification or erasure of valuable data on a device. Most commercial software, audio and video is sold pre-protected.


These mechanisms are intended to prevent only accidental data loss or attacks by computer viruses. A determined user can easily circumvent them either by covering a notch with adhesive tape or by creating one with a punch as appropriate, or sometimes by physically altering the media transport to ignore the write-protect mechanism.

Write-protection is typically enforced by the hardware. In the case of computer devices, attempting to violate it will return an error to the operating system while some tape recorders physically lock the record button when a write-protected cassette is present.

Write blocking

Write blocking, a subset of write protection, is a technique used in computer forensics in order to maintain the integrity of data storage devices. By preventing all write operations to the device, e.g. a hard drive, it can be ensured that the device remains unaltered by data recovery methods.

Hardware write blocking was invented by Mark Menz and Steve Bress (US patent 6,813,682 and EU patent EP1,342,145)

Both hardware and software write-blocking methods are used; however, software blocking is generally not as reliable.


    http://www.patentstorm.us/patents/6813682.html (US patent 6,813,682)

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