Forensic disk controller

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). A device which is installed between a storage media under investigation and an investigator's computer is called a "bridge kit". The bridge kit has one connector for the storage media and another connector the investigator's computer. It allows the investigator to read, but not alter the device under investigation. The United States National Institute of Justice operates a Computer Forensics Tool Testing (CFTT) program which formally identifies 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. 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.