Most large software releases – operating systems, office suites and anything else big enough to use an entire CD-ROM disc – are transferred legally (or illegally) in the form of disk images. These are single files (which usually have the extension .ISO, hence “ISO file) that contain the entire contents of the CD or DVD disc with extra “metadata” included – such as the discs’ name and boot information, if required. This allows the end-user to put a blank disc in their drive, open his or her software burning program and click “Burn Image” and end up with a CD full of stuff in just a few minutes. In a nutshell, I can create a CD-ROM named “Pictures” with a variety of digital images on it, create an .ISO file of the disc that I can distribute to anyone, who can then create a million discs just like mine – or send it on to someone else who can then make a million copies of their own.
This is not new. The Linux operating system has been distributed this way for ages. Microsoft rarely mails actual CDs of beta software to testers these days and instead opts to allow users to download ISOs of the beta program – like Windows Server 2008 for example. But what good are the image files aside from allowing users to make flawless copies of CD or DVD discs?