Systems Security CHAPTER 1 13 incredibly tiny pits or bumps on the surface of the disk. The different types of disks include: CD-R, which is short for CD-Recordable. This type of CD is a Write Once, Read Multiple (WORM) media that allows you to record data to it once, so that you can later read the data. Once data is written to a CD-R, no additional data can be written to the CD. CD-RW, which is short for CD-Rewritable and allows you to erase and write to the disk multiple times. CD-ROM is an acronym for Compact Disk--Read Only Memory; how- ever, the term has grown to refer to the CD-ROM drive used to read this optical storage media. CD-ROMs are capable of holding up to 700 MB of data and remain a common method of storing data. CD and DVD media are unaffected by Electromagnetic Pulse (EMP) effects, X-rays, and other sources of electromagnetic radiation. The primary consideration with recordable CD media (and to a lesser extent, manufactured media) is energy transfer. It takes a significant amount of energy to affect the data that the writing laser transfers to the disk. Rewritable disks (discussed later) require even more energy to erase