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What is the best way to safely and permanently delete files from a hard drive?

Posted By : Student of Katharine Gibbs School - New York on September 11, 2003

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What is your recommendation for safely disposing of information of old computers? Can the passwords, etc. I enter on the internet be read on my hard-drive even after I exit?

Consumer Reports October 2003,page 15, regarding it is not safe to donate your computer even if the hard drive is wiped clean:

"Raiding your old computer. According to a recent study MIT graduate students were able to recover sensitive files from hard drives on one-third to half of the used computers they tested.

The fix: Businesses and indivudals should use hard-drive shedding software or remove and destroy hard drives before discarding a personal computer."

Thanks for your help, Andrea Pasztor

This question was answered on September 11, 2003. Much of the information contained herein may have changed since posting.

The most common way to delete files in Windows and Macintosh is to drag the file into the Mac "trash can'' or Windows "recycling bin.'' While that removes it from the desktop it does not remove it from the computer In fact, you can restore the file by simply opening the trash or recycling bin and dragging it back to the desktop.

Both the Mac and Windows allow you to go one step further by emptying the trash which appears to delete the file completely The Mac, for example, asks you if you are sure "you want to remove the item in the trash permanently.'' Windows asks if you're "sure you want to delete all of the items in the recycling bin.''

But neither method is permanent Erasing a file doesn't actually delete the data; it just removes the file name from the directory The data is still there Deleting a file the standard way is a bit like crumpling up a piece of paper and throwing it in the trash can rather than running it through a shredder The MS-DOS delete command doesn't have an obvious "undo'' feature but it too can easily be reversed.

formatting a hard disk sure seems like a pretty good way to obliterate your data, but it's not The Windows Format command will warn you that "Formatting will erase ALL data on this disk,'' but, again, that's not entirely true While it will make the disk appear to be empty, that data itself will not be erased The same is true with the fdisk command which creates and deletes hard drive partitions There are numerous programs that can bring back seemingly eradicated from formatted hard drives "Recover it All'' from DTI Data advertises that it can "Recover data lost due to Format, Fdisk, virus attack, deletion and many other scenarios.''

Someone looking to gather your personal information from a discarded disk drive doesn't even need any particularly expensive or exotic software The popular Norton System Works includes Norton UnFormat and Norton UnErase that can often do the trick But you don't even have to spend anything to get your hands on such software If you visit the File & Disk Management section of, you'll find numerous "free to try'' programs designed to recover deleted files or formatted disks.

In addition to the files that you know about, your hard disk may contain personal information in "temporary'' files such as a browser or print spooler cache These files are created automatically but they are not necessarily deleted automatically Another source of "hidden'' personal information includes e-mail programs which sometimes archive your incoming and outgoing messages.

Unless you're engaged in international espionage, sanitizing a drive by overwriting the data is probably adequate protection but it is theoretically possible for someone with the resources of the National Security Agency to recover the data using very sophisticated methods and equipment.

Still, Garfinkel and Shelat refer to these extraordinary methods as "exotic'' and conclude that "simply overwriting user data with one or two passes of random data is probably sufficient.''

"Sure Delete,'' from Wizard Industries ( is a free program that uses a wizard interface to give you a "clean, secure, evidence-free hard drive in a matter of minutes.''

Macintosh OS X users can download a free copy of SafeShred from CodeTek Studios ( which claims to provide ``a virtual file shredder'' that completely shreds the file For $15 you can buy ShredIt from Mireth Technologies ( for Macintosh OS 8/9 as well as OS X

Drive Scrubbers

Autoclave - Secure Disk Deletion Free

Erase Delete Erasure Wipe & Overwrite by CyberScrub $39.95

Data Scrubber from Data Devices International $1695

PowerQuest Corporation - Proven Solutions for Storage Management $90

Eraser Free

DataEraserâ„¢ Software - $30 to $500

AccessData - WipeDrive $39.95

UniShred Pro - Secure Disk Overwriting $450

Wipe Secure File Deletion (Linux) Free

Wiperaser XP $24.95

Source: Simson Garfinkel and Abhi Shelat

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Posted by Student of Katharine Gibbs School - New York on September 11, 2003

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