Do you delete all the files before selling your out-of-date company computer? Do you remove the original document from the copier machine after you make a copy? Do you take your sensitive information away from the fax machine after you have faxed it to someone else?

You probably answer yes to all or most of these questions, and you probably think you have done everything necessary to protect your important company information. Well, guess again.

Deleting files from a computer's hard drive simply makes the space on the drive available for a new file to be saved - it removes nothing from the drive itself. All the e-mail, address lists, payroll information, private correspondence, financial worksheets, and everything else you store on your computer is still there when you think you are deleting the files.

Cartridges from printers and fax machines that use thermal-transfer or dye-sublimation technology retain images after the print or fax job is completed. Throw these cartridges in the trash without destroying them and you might as well leave the original document out where others can see it. And interestingly, the number of machines that use these types of cartridges is increasing.

How should companies deal with these security breaches that are waiting to happen? Security Management Online provides tips for determining if your printer and fax cartridges are able to retain images.

If you are planning on discarding or selling used computer equipment, it is recommended that you acquire a disk erasing program which will completely remove all trace of data on the hard drive. Alternatively, some suggest removing and destroying the hard drive and selling the computer without the drive.