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A forensic disk controller or hardware write-block device is a specialized type of computer hard disk controller made for the purpose of gaining read-only access to computer hard drives without the risk of damaging the drive's contents. The device is named forensic because its most common application is for use in investigations where a computer hard drive may contain evidence. Such a controller historically has been made in the form of a dongle that fits between a computer and an IDE or SCSI hard drive, but with the advent of USB and SATA, forensic disk controllers supporting these newer technologies have become widespread. Steve Bress and Mark Menz invented hard drive write blocking (US Patent 6,813,682). The United States National Institute of Justice operates a Computer Forensics Tool Testing (CFTT) program which formally identifies〔http://www.cftt.nist.gov/HWB-ATP-19.pdf〕 the following top-level tool requirements: *''A hardware write block (HWB) device shall not transmit a command to a protected storage device that modifies the data on the storage device.'' *''An HWB device shall return the data requested by a read operation.'' *''An HWB device shall return without modification any access-significant information requested from the drive.'' *''Any error condition reported by the storage device to the HWB device shall be reported to the host.'' ==Description== Forensic disk controllers intercept write commands from the host operating system, preventing them from reaching the drive. Whenever the host bus architecture supports it the controller reports that the drive is read-only. The disk controller can either deny all writes to the disk and report them as failures, or use on-board memory to cache the writes for the duration of the session. A disk controller that caches writes in memory presents the appearance to the operating system that the drive is writable, and uses the memory to ensure that the operating system sees changes to the individual disk sectors it attempted to overwrite. It does this by retrieving sectors from the disk if the operating system hasn't attempted to change them, and retrieving the changed version from memory for sectors that have been changed. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Forensic disk controller」の詳細全文を読む スポンサード リンク
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