Chapter 8 - CD and DVD Forensics

Abstract

Digital versatile discs (DVDs) are an evolutionary growth of compact disc (CD's) with slight changes. Both CDs and DVDs are electro optical devices. There are no magnetic fields in the reading or recording of these discs, therefore, they are immune to magnetic fields of any strength, unlike hard drives Due to its immunity to magnetic fields, CD and DVD media is 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 is important to understand that CD and DVD media is read with light, and recordable discs are written with heat. Using an infrared (ILK) laser, data is transferred to a CD or DVD onto a small, focused area that places all of the laser energy onto the target for transfer. It should be noted that all CD and DVD media are sensitive to heat, and recordable media is sensitive to IR, ultraviolet (UV), and other potential intense light sources. Some rewritable media are affected by EPROM erasers, which use an intense UV light source. Various forensic alternative light sources can provide sufficient energy to affect optical media, especially if it is focused on a small area It is not necessarily a question of heat but one of total energy transfer, which can result in heating.