First lets look at what happens to data once is has been put into that recycling bin or trash can. This goes for all computers, not just macs. When something is deleted it is not zeroed out or actually deleted. Zeroed out or random data overwrite? Let's step back again. All data is made up of 1s and 0s. This is binary code. Now, to make up a document that lets say is 2 pages long will take up tens of thousands of these 1s and 0s to hold the data of the file.

So, now lets take this up a notch. All the files you see on your computer are visually represented by little icons - or documents or whatever you click on. These are only visual keys that tell the computer to access a point on the computer where it will find the data related to that document. Remember, everything on the computer is virtual - nothing is real. So this icon is not the data, but only a bridge to the data somewhere on your hard drive. When this icon is put in the trash/recycling bin the bridge is the item being deleted. Not the data! It feels the same - out of sight, out of mind. But it's still there (or could still be there).

But what if you want to delete a sensitive document? Well there's lots of ways to go about it. On a Mac, you have two options, you can simply just empty the trash. All this does is deletes the linking file to the data but the data stays on your hard drive. This is why it is so quick and tens of thousands of documents can be deleted in seconds. Secure Empty Trash on the other hand will erase your data and overwrite it so that it is unrecoverable to most. If you want to ensure your data is securely erased then you should open up Disk Utilities - a free application provided by Apple. Click the hard drive you want to erase the free disk space. Under the Erase tab click 'Erase Free Space'. You'll be given 3 options, zeroing out, 7 passes and 35 passes.

Generally speaking there are 3 types of erasing data that are commonly used. The first is a single pass. Sometimes this is reffered to zeroing out. The data being erased will be either rewritten with random data or all zeros. The zero method is the quickest way to erase data and for 99% of us good enough for our purposes.

The second method is 3 passes to 7 passes. This is used only when you need to erases extreamly sensitive data. The data is passed by 3 or 7 times with random data creating an unreadable and highly encrypted series of 1s and 0s that to at least the DOD (Department of Defense) is considered securely deleted.

Now the last and most secure method is the 35 pass routine - also known as the Gutmann algorithm. Gutmann had a theory that data could be read and extracted even after it had been passed by and written over with new data. The science behind this is that if a 1 is written, then a 0 is written on top of that 1 there would be a slight discrepancy with the 0. Because magnetic platters are not perfect, the -1 to make the 0 would be more like a -0.95 and therefore create a 0.05 instead of a 0. Now I'm not refering to a new binary, just that the zero (meaning no magnetic field) would have a slight residue left behind. Now your data must be really important to go to this trouble of recovering data in this manor.

Maybe if you had proof that god did or did not exist on your hard drive and you didn't want anyone to find out you'd want to erase it like this. But for any other reason, this is just over kill. It just sounds cool to pass over your data with 5 sets of random data, 25 sets of 101010, 000000, 111111 and many other patterns, then 5 more sets of random. If you're going to accomplish anything by doing this, you're guaranteed to cause some ware and tear on your drive. So don't waste your time or hard drive life with 35 passes.

If you're really serious about deleting everything on your drive, just remove it and toss it into a machine shredder! That will break your platter into millions of tiny pieces that will never be recovered - by anyone. It's a lot quicker then the 35 passes too. If you're using a PC then here's a quick list of some utilities that will preform the erase passes mentioned above. Remember, for 99% of us, a single pass is more then enough. If you're just trying to keep your younger brother from finding the secret door to your tree house you probably don't even need to worry about that! Just put your need into perspective and remember that the military uses 3 passes.

Window Washer - Webroot Software Quote: Window Washer washes away your online and offline computer activities, giving you more privacy and increasing your PC's performance. It cleans areas such as the cache, cookies, file history, and Registry items. Window Washer offers customizable features that let you control what gets washed and what stays. This program also gives you the ability to schedule washes of your system when it's most convenient for you. Version 6.5 is now Windows Vista compatible, it can be set to clean your computer on a regular schedule, and it securely removes files using government standards.

Folder Lock - New Softwares Quote: Folder Lock is a fast file encryption software that can also password protect folders, lock files and protect USB Drives and lock CD/DVDs. Folder Lock creates encrypted storages called 'Lockers'. You can keep as many of your private files and folders in your Locker and password protect it with a single click. You can transfer, secure and backup these Lockers. Lockers are portable, you can keep them in USB Drives, CD/DVD, & notebooks or transfer them via email or upload. These Lockers are undeletable on the computer where Folder Lock is installed. You can create as many Lockers as you want. Different users can create different Lockers with different passwords as well. With Folder Lock, you can choose either to encrypt using 256-bit AES on-the-fly encryption or lock files, folders and drives anywhere on your computer. Each Locker can contain your encrypted files as well as your personal list of locked items. Furthermore, Folder Lock's options like hack monitoring, stealth mode, data shredding, history cleaning, auto protection, portable USB autoplay feature & virtual keyboard can enhance file locking and encryption beyond anything ever achieved. In addition, a locker's delete, move and rename are password protected to prevent data loss.

Glary Utilities Pro - Glaryutilities Quote: Glary Utilities Pro offers numerous and easy-to-use system tools and utilities to fix, speed up, maintain, and protect your PC. It allows you to clean common system junk files, as well as invalid registry entries and Internet traces. You can manage and delete browser add-ons, analyze disk space usage and find duplicate files. You can also view and manage installed shell extensions, encrypt your files from unauthorized access and use, split large files into smaller manageable files and then rejoin them. Furthermore, Glary Utilities Pro includes the options to optimize memory, find, fix, or remove broken Windows shortcuts, manage the programs that start at Windows startup and uninstall software. Other features include secure file deletion and an Empty Folder finder.

Freeraser: Free Shredder - Simple file shredder with three options, 1 round, 3 rounds and the 35 round using the Gutmann algorithm.

Eraser Secure Data Removal Tool - Comes with a variety of space saving and memory swap tools. This program gives you the option of random writing data over as many or as few times as you'd like. The program suggest between 3 and 7 based on the US Department of Defense (DOD) protocols. This application is also open source.

SysInternals SDelete - This command line utility comes with a variety of tools including overwriting a disks unused disk space. It allows you to pass as many times over the data as you'd like and includes the clearing standard DOD 5220.22-M from the Department of Defense.

Darik's Boot and Nuke (DBAN) - When selling your computer on ebay this is a safe way to ensure your data won't get into the wrong hands. This little application is designed to destroy all information on your computer. It can be used in emergancy situations where you find the need to obliterate all your data in a panic. The application comes with a bootable disk and once activated it will automatically destroy all the information on your hard disk.

OverWrite - This is a General Public License application that overwrites data with random data.

Other great applications are: Eraser, Recover Files, Wipe Secure File Deletion, Secure Delete, Autoclave.