Number 209 - October 2000

Just How Well Does That "DELETE" Button Work?
by Kim Komando via May 2000 Data Line
There are many legitimate situations where you'd want to make sure a deleted computer file is really deleted. This could be an e-mail message, a word processing file, or maybe even a Web page. The problem is that in most cases, when you think you've deleted a file, you've really left most--if not all--of it intact.     Let's take the case of an e-mail message sitting in your inbox. When you click the Delete button in your e-mail program, all that usually does is move the message from the inbox to the "Deleted Items" or "Trash" folder; the message really isn't deleted at all. To delete it permanently, you have to select it while it's in the "Deleted Items" or "Trash" folder and then click the Delete button a second time.     However, that might not even be enough. Do you perform regular system backups, automatically or manually? (If you don't, you should, but that's for another column. ) If you backup your e-mail files before you permanently delete the e-mail message in question, there will still be a record of that message in your backups.     If that presents a problem in your particular situation, you have two options. Depending on the nature of the backup, you may be able to edit the files and remove the unwanted message. Otherwise, you may want to make sure you don't need anything from that backup and then take a new backup, destroying the older version.     What about surfing the Web? Today's Web browsers want to make your Internet experience as smooth and hassle-free as possible. To that end, they go out of their way to remember where you've traveled online and hold onto files you may need when you go back to those sites. That means there may be a complete record of where you've surfed, even after you've long since closed a particular Web page.     How do you get rid of these leftover files? That depends on which browser you're using. For example, in Netscape Navigator 4.7 , you need to select Preferences from the Edit menu. In the same window you use to specify your home page, you'll see two buttons near the bottom. One is labeled "Clear History" and the other is labeled "Clear Location Bar." Click both of these buttons and Navigator will forget everything it's remembered about where you've been surfing.     The technique for Internet Explorer 5 is very similar. First, select Internet Options from the Tools menu. Then on the General tab, click the "Delete Files" button, as well as the "Clear History" button. This gives Internet Explorer a case of permanent amnesia.     That's all well and good, but what about regular data files--word processing documents, spreadsheets and the like? Deleting them is simple, isn't it? You just drag them to the Trash/Recycle Bin, and then empty the whole thing out. The file's gone just like that, right? Well, not exactly.     Have you ever wondered how programs such as Norton Utilities can "undelete" a file that you deleted	by mistake? Let me explain how that works, and in the process, explain why deleting a file doesn't really delete all the data in that file.     When you create any file on your hard drive, a marker is placed at both the beginning and the end of the file. Anything in between those two markers comprises the actual contents of the file. As long as those markers exist, your computer knows not to try to store any other data in the space occupied by that file.     When you delete a file, your computer wants to get you on your way as soon as possible. So instead of deleting the entire file, your computer simply removes those markers, leaving the actual file data relatively intact. However, with the markers gone, the hard drive knows it's okay to use that physical space for some other file. The end result is that the file data isn't really wiped out until the hard drive puts something else in its place.     This is why "undelete" utilities have virtually a 100-percent success rate when you run them immediately after an unintentional deletion. Since you haven't had a chance to overwrite the old data with new data, these programs can figure out where the markers were and then put them back.     The flip side, of course, is that if simply delete a file, there's a pretty good chance that someone else can come along and reconstruct using one of the utility programs.     The question then becomes: How do you make sure a file is totally and permanently deleted.     One of the easiest ways--although not always 100-percent effective--is to simply defragment your hard drive. You can use the Defrag program that comes with Windows, or a commercial program like Speed Disk, which is part of the Norton.     When you defragment your hard drive, you rearrange the physical locations of all the files on your hard drive for optimum drive performance. Since virtually all of your files get moved during this process, the chances are high that any leftover data from deleted files will be overwritten.     But, there's no guarantee here. If there's not much fragmentation on your hard drive, the defrag program may not move enough files around to make a difference.     The best way to make sure files are permanently deleted is to use a program specifically designed for that purpose. The Norton Utilities includes one called Wipe Info. Power Desk Utilities 98 (from OnTrack Data International, www.ontrack.com ), offers a similar feature. Finally, if you're on a budget, you can download BCWipe (Jetico, www.jetico.com). This program is free for non- commercial use and is available for both Windows 98 and Linux. You should know, though, that when the government wants to be sure top secret files are permanently erased from a computer's hard drive, they just don't simply wipe the disk clean. They actually take a hammer in hand and smash the hard disk into pieces.
Number 209 - October 2000