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Deleted, but not gone

MAINTAINING privacy in the era of digital information requires work on a number of fronts, whether fending off spyware, protecting important files with encryption or configuring a Wi-Fi hot spot to keep interlopers off a wireless network. Deleting confidential data completely is essential when donating or selling old computers. It can also help maintain privacy on computers that may be lost or stolen. For businesses looking for ways to comply with the security requirements of laws like the Sarbanes-Oxley Act, a sound policy on data control and destruction is crucial.

When normal deletion methods like the Recycle Bin or the delete command are used, the computer’s operating system, for the sake of speed, creates an illusion that data has been deleted. It merely earmarks that region of a disk or drive as being available for new data to overwrite the old data. Until that overwriting occurs, the old data can be retrieved with undelete programmes and tools used by data recovery labs and law enforcement agencies. There are, however, several options for securely eliminating data from hard disks, USB flash drives and other storage media. These programmes overwrite data with meaningless characters to render it unrecoverable with today’s data recovery techniques. Some of the programmes can overwrite entire drives, while others can single out individual files or other information saved by a computer’s operating system or programmes like Web browsers.

Shredding machines that can destroy diskettes, CD’s and DVD’s are also available. Several programmes are available to overwrite entire hard disks.

Darik’s Boot and Nuke, known also as DBAN, is a free open-source programmes available at It runs on Windows computers and offers six methods to overwrite data, including a Defense Department standard (DoD 5220.22-M). It can overwrite the disk three times and a method called PRNG Stream Wipe, which can make a user-defined number of disk overwrites using randomly generated characters.

The programme, available in two formats, can be burned to a CD or copied to a diskette. After a computer is started with either type of disk inserted, DBAN’s menu will load. (The computer’s boot device order, located in the BIOS, may need to be adjusted to load disk-wiping programmes, which run their own operating systems.) According to its author, Darik Horn, the programme’s coding can be scrutinised by anyone, which can help assure reliability. Horn said a single overwrite should be enough to render data unrecoverable, but he recommends at least four overwrites to guard against possible future advancements in data recovery techniques and other unknowns. Another programme for wiping entire disks on Windows computers is WipeDrive from WhiteCanyon ( It offers 12 overwriting methods, including the Defense Department standard with three overwrites. Although the company’s president and chief executive, Steve Elderkin, said methods that use a single pass are enough to render data unrecoverable. More than one overwrite is a good idea for disks more than five years old and for smaller drives, Elderkin said. The programme can examine all sectors of a disk to verify whether overwriting was successful. WhiteCanyon also offers MediaWiper, a programme that can overwrite data on removable storage devices like USB flash drives, memory cards, diskettes, Zip drives and external hard drives connected to USB and FireWire ports. It offers four overwriting methods, including an option with 12 passes. It also has a verification feature that can examine all sectors of a drive.

Macintosh computers come with a tool to erase entire disks and attached drives. The feature, called Disk Utility, is included in the Utilities folder, and also on the system installation DVD or CD. For example, Window Washer from Webroot Software ( includes a feature called bleaching that offers several overwriting methods, including a National Security Agency standard of seven overwrites, and the Gutmann standard of 35 overwrites.

With bleaching enabled, Window Washer can securely delete individual files, folders and contents of the Recycle Bin. It can also overwrite free space on drives, which may contain old data from files deleted by using routine methods.

Another file-shredding programmes, called ShredIt, is available in versions for both Windows and Macintosh computers from Mireth Technology ( The programme’s overwrite methods include user-defined options with up to 35 passes. Another useful feature, in the Macintosh version, is the option to overwrite rewritable CD’s. Other deleting files securely programmes are Acronis Privacy Expert Suite from Acronis (, and PGP Desktop Home ( from the PGP Corporation. For Mac users, the Mac OS X operating system (version 10.3 and up) has a tool called Secure Empty Trash that deletes individual files in the trash using the Defense Department standard with seven overwrites.

Several shredders available are the Royal MD100 Media Destroyer ( and the Powershred PS-70 from Fellowes ( shreds CD’s and DVD’s, accepts 14 sheets of paper at once, and can shred credit cards, staples and small paper clips. One way to ensure that data on a hard disk will never be recovered is to destroy the disk. You can do that by removing the disk’s platters and grinding them to bits – extreme, but effective.

Article by *Thomas J. Fitzgerald*

This entry was posted on Tuesday, November 8th, 2005 at 5:19 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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