"An investment in knowledge pays the best interest."
Benjamin Franklin
Most Microsoft Windows users know that when they delete a file in Windows Explorer it goes to the Recycle Bin. This means the file is still present on your hard drive, it is just removed from your “active files” list. If you delete a file by accident, you can go into the Recycle Bin and restore the file. This is a handy little safety measure that Microsoft has included in Windows 95 and above.
This is also the first security issue concerning deleted files. If you delete personal or sensitive information to the Recycle Bin, and then don’t finish the process by removing it from the Recycle Bin, that information is still present on your hard drive and easily retrievable by anyone with access to your system.
Empty your Recycle Bin on a regular basis. To most this may seem like an obvious statement, but to others it may not be. I know more than one person who rarely, if ever, empties their Recycle Bin. It seems to me that the only time their Recycle Bin gets emptied is when they call me to come work on their computer for some reason and I empty it.
If you don’t feel that security is an issue because you don’t have any personal or sensitive information on your machine to delete, there is another reason for keeping your Recycle Bin emptied. Space. Those files you hold in your Recycle Bin needlessly take up space on your hard drive. Keeping your Recycle Bin cleaned out will regain all that valuable disk space for your system to use. Besides, if you want to hang on to these files, why delete them in the first place?
Our second security issue comes to light the moment you click the command to “Empty Recycle Bin.” You may be under the impression that those files are now gone for good and cannot be recovered by anyone. This is not true. Your files are still there on your hard drive and intact.
In order to understand why this is, we need to take a brief look at how data is stored on your hard drive. I’ll try to keep this explanation simple and not too technical.
Each time you click the “Save” option to save your work, this data is written to your hard drive. Over time, you can just imagine the number of files (literally thousands) being created on your hard drive. In order for Windows to be able to find these files again quickly and without errors, it needs an organized way of keeping track of them. Fortunately for us, there is an organized way for Windows to do this.
When Windows writes data to your disk drive, it puts the data in “containers” called clusters or blocks. Depending upon the size of your disk and the file system Windows is using, these containers are all set to a specific size (up to a maximum of 32 kilobytes). If your data is less than the size of the container, Windows will go to the first available container and put your data in it. But if your data is larger than the container size, Windows divides up your data over several containers. It goes to the first available container and fills it up, then goes to the next available one and fills that one up, and goes to the next, and so on until all your data is written to the drive.
In order to keep track of what container(s) it has placed your data in, when Windows formats your hard drive it assigns each of these containers a number in order to identify it (we won’t worry about the details of this numbering system here, since it has no affect on understanding the file deletion process). Windows then creates a table, called a File Allocation table (FAT), it uses to index the locations of all the data it has written to your drive. When your data file is actually saved to disk, Windows will then index so it knows where to find the file again.
table 1 below provides an example of how the file allocation table works when saving your data to your hard drive. The two columns on the left represent the File Allocation table. The column on the far right represents the actual data that is saved on your hard drive.
|
File |
Container # |
Hard drive |
|
File1 |
1 |
1011100101 |
|
File2 |
2 |
0101011010 |
|
File2 |
3 |
1010111101 |
|
File3 |
4 |
1110001010 |
Fig. 1
Notice that when file1 was saved, Windows went to the first available container and placed the file there, then it entered the file name in the table so it knew that file1 was placed there. When file2 was saved, Windows went to the next available container (container 2) and began saving the file there. But file2 was larger than the container, so Windows had to place the balance of the file in the next container (container 3) and made the two entries in the table so it would know that the file was in these two containers. The next file that needed to be saved (file3) was then saved in container 4, the next available container, and the entry made in the table.
Now, when you want to open one of these files, all Windows has to do is look at the File Allocation table to find out where to look on your hard drive to find the file. But what happens when you want to delete a file?
Continue... 
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