DRM?
Digital rights management.
It is the technology that prevents you from copying a DVD or putting an iTunes song on anything but an apple player.
Most DRM can be circumvented and it is probably/maybe legal for personal use at this time.
“Digital Rights Management”
The means to prevent you from copying the works you bought. DVDs have this in the form of CSS. Just copying the files from the DVD to your hard drive will normally result in unplayable files. The encryption of CSS must first be cracked. That’s easy, but illegal, even if you’re making a backup (normally legal) or format shifting (also normally legal) to your hard drive or iPod.
DRM has been severely abused for anticompetitive means and used to take away our fair use rights to copyrighted materials.
We already have an industry-purchased law enforcing DRM called the DMCA. This will go even further.