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Acknowledgments
Syngress would like to acknowledge the following people for their kindness
and support in making this book possible.
Syngress books are now distributed in the United States and Canada by
O’Reilly Media,Inc.The enthusiasm and work ethic at O’Reilly are incredible,
and we would like to thank everyone there for their time and efforts to bring
Syngress books to market:Tim O’Reilly,Laura Baldwin,Mark Brokering,Mike
Leonard,Donna Selenko,Bonnie Sheehan,Cindy Davis,Grant Kikkert,Opol
Matsutaro,Steve Hazelwood,Mark Wilson,Rick Brown,Tim Hinton,Kyle
Hart,Sara Winge,Peter Pardo,Leslie Crandell,Regina Aggio Wilkinson,Pascal
Honscher,Preston Paull,Susan Thompson,Bruce Stewart,Laura Schmier,Sue
Willing,Mark Jacobsen,Betsy Waliszewski,Kathryn Barrett,John Chodacki,
Rob Bullington,Kerry Beck,Karen Montgomery,and Patrick Dirden.
The incredibly hardworking team at Elsevier Science,including Jonathan
Bunkell,Ian Seager,Duncan Enright,David Burton,Rosanna Ramacciotti,
Robert Fairbrother,Miguel Sanchez,Klaus Beran,Emma Wyatt,Krista
Leppiko,Marcel Koppes,Judy Chappell,Radek Janousek,Rosie Moss,David
Lockley,Nicola Haden,Bill Kennedy,Martina Morris,Kai Wuerfl-Davidek,
Christiane Leipersberger,Yvonne Grueneklee,Nadia Balavoine,and Chris
Reinders for making certain that our vision remains worldwide in scope.
David Buckland,Marie Chieng,Lucy Chong,Leslie Lim,Audrey Gan,Pang Ai
Hua,Joseph Chan,June Lim,and Siti Zuraidah Ahmad of Pansing Distributors
for the enthusiasm with which they receive our books.
David Scott, Tricia Wilden, Marilla Burgess, Annette Scott, Andrew Swaffer,
Stephen O’Donoghue,Bec Lowe,Mark Langley,and Anyo Geddes of Woodslane
for distributing our books throughout Australia, New Zealand, Papua New
Guinea,Fiji,Tonga,Solomon Islands,and the Cook Islands.
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Author
Paul Crowley is the founder and lead developer at InfinaDyne.
InfinaDyne is one of a small number of companies publishing soft-
ware specifically targeted at the forensic examiner.Paul has been
working in the software development field since 1975.His career
includes experience that spans computer hardware from the very
smallest home video-game console to the largest IBM mainframes.
Paul began working with CD recording technology in 1994 and is
one of a small number of respected authorities on this technology.
The first CD data recovery software product was written by Paul
and has led the market for such tools since 1997.InfinaDyne has
been offering CD and DVD Forensics training classes since 2005
and has held classes in the U.S.and Australia.Attendees at these
classes have included members of the FBI,US Department of
Defense,and the Australian Federal Police.
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Technical Editor
Dave Kleiman (CAS,CCE,CIFI,CISM,CISSP,ISSAP,ISSMP,
MCSE) has worked in the information technology security sector
since 1990.Currently,he is the owner of
SecurityBreachResponse.com and is the Chief Information Security
Officer for Securit-e-Doc,Inc.Before starting this position,he was
Vice President of Technical Operations at Intelliswitch,Inc.,where
he supervised an international telecommunications and Internet ser-
vice provider network.Dave is a recognized security expert.A
former Florida Certified Law Enforcement Officer,he specializes in
computer forensic investigations,incident response,intrusion anal-
ysis,security audits,and secure network infrastructures.He has
written several secure installation and configuration guides about
Microsoft technologies that are used by network professionals.He
has developed a Windows operating system lockdown tool,S-Lok
(www.s-doc.com/products/slok.asp ),which surpasses NSA,NIST,
and Microsoft Common Criteria Guidelines.
Dave was a contributing author to Microsoft Log Parser Toolkit
(Syngress Publishing,ISBN:1-932266-52-6).He is frequently a
speaker at many national security conferences and is a regular con-
tributor to many security-related newsletters,Web sites,and Internet
forums.Dave is a member of several organizations,including the
International Association of Counter Terrorism and Security
Professionals (IACSP),International Society of Forensic Computer
Examiners® (ISFCE),Information Systems Audit and Control
Association® (ISACA),High Technology Crime Investigation
Association (HTCIA),Network and Systems Professionals
Association (NaSPA),Association of Certified Fraud Examiners
(ACFE),Anti Terrorism Accreditation Board (ATAB),and ASIS
International®.He is also a Secure Member and Sector Chief for
Information Technology at The FBI’s InfraGard® and a Member
and Director of Education at the International Information Systems
Forensics Association (IISFA).
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Introduction
This book was originally developed as a companion for the CD and DVD
Forensics class given through InfinaDyne. It has been researched and prepared
by Paul Crowley,the founder and lead developer at InfinaDyne. InfinaDyne is
one of a small number of companies publishing software specifically targeted at
the forensic examiner.
Paul Crowley has been working in the software development field since
1975. His career includes experience that spans computer hardware from the
very smallest home video-game console to the largest IBM mainframes.
Crowley began working with CD recording technology in 1994 and is one of a
small number of respected authorities on this technology.
InfinaDyne publishes the product CD/DVD Inspector which is featured in
this book. It was developed based on a data recovery program,originally
written in 1996,to assist users of CD recording in the recovery from hardware
errors,software bugs and user mistakes. Today,CD/DVD Inspector is one of a
small number of products which professional forensic examiners worldwide rely
on to acquire evidence from CD and DVD media.
For the purposes of this book,all examples and practical exercises are based
on CD/DVD Inspector version 3. Earlier versions of the product may not be
capable of performing all of the functions described in the examples. Later ver-
sions of the product should be able to be used without any difficulties.
If you or your organization is interested in the CD and DVD Forensics
training class please contact the InfinaDyne sales department for more informa-
tion at sales@infinadyne.com.
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xxii Introduction
Conventions in this Book
The term “disc”will be used to refer to optical media (CDs and DVDs) and
“disk”to refer to hard drives and other magnetic media.
An effort has been made to reproduce all measurements in both metric and
US terms.
A “nanometer”is a measure of length. It is equal to one billionth of a
meter. One million (1,000,000) nanometers equal one millimeter.
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Chapter 1
Physical
Characteristics of
CD and DVD Media
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2 Chapter 1 • Physical Characteristics of CD and DVD Media
Little has changed in Compact Disc (CD) physics since the origin of CD
audio discs in 1980.This is due in part to the desire to maintain physical
compatibility with an established base of installed units,and because the struc-
ture of CD media was both groundbreaking and nearly ideal for this function.
Digital Versatile Discs (DVDs) are an evolutionary growth of CD’s with
slight changes.Considering the development of DVD follows the CD by 14
years,you can see that the CD was truly a revolutionary creation in its time.It
is important to understand that both CDs and DVDs are electro optical devices,
as opposed to nearly all other compter peripherals which are electromagnetic.
There are no magnetic fields in the reading or recording of these discs,there-
fore,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 electro-
magnetic radiation.The primary consideration with recordable CD media
(and to a lesser extent,manufactured media) is energy transfer.It takes a sig-
nificant amount of energy to affect the media that the writing laser transfers
to the disc.Rewritable discs (Compact Disc - ReWriteable [CD-RW],
Digital Versatile Disc - Rewriteable [DVD-RW],and Digital Versatile Disc -
Rewriteable [DVD+RW]) require even more energy to erase or rewrite data.
This is in direct contrast to floppy disks and hard drives,which can be
affected by electromagnetic devices such as Magnetic Resonance Imaging
(MRI) machines,some airport X-ray scanners,and other devices that create a
strong magnetic field.CDs and DVDs are also immune to Electromagnetic
Pulse (EMPs) from nuclear detonations.
It is important to understand that CD and DVD media is read with light,
and recordable discs are written with heat.Using an infrared (IR) 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 (i.e.,above 120F/49C),and recordable media
is sensitive to IR,ultraviolet (UV),and other potential intense light sources.
Some rewritable media are affected by Erasable Programmable Read-Only
Memory (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.
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Physical Characteristics of CD and DVD Media • Chapter 1 3
Both CD and DVD media are organized as a single line of data in a spiral
pattern.This spiral is over 3.7 miles (or 6 kilometers [km]) in length on a CD,
and 7.8 miles (or 12.5 km) for a DVD.The starting point for the spiral is
towards the center of the disc with the spiral extending outward.This means
that the disc is read and written from the inside out,which is the opposite of
how hard drives organize data.
With this spiral organization,there are no cylinders or tracks like those on
a hard drive.(The term “track”refers to a grouping of data for optical media.)
The information along the spiral is spaced linearly,thus following a pre-
dictable timing.This means that the spiral contains more information at the
outer edge of the disc than at the beginning.It also means that if this infor-
mation is to be read at a constant speed,the rotation of the disc must change
between different points along the spiral.
All optical media is constructed of layers of different materials (see Figure
1.1).
Figure 1.1 CD-R Construction
This is similar to how all optical media discs are constructed.The differ-
ences between different types of discs are:
■ CD-RThe dye layer can be written to once.
■ CD-ROMThe reflector has the information manufactured into it and
there is no dye layer.
■ CD-RWThe dye is replaced with multiple layers of different metallic
alloys.The alloy is bi-stable and can be changed many times between
different states.
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4 Chapter 1 • Physical Characteristics of CD and DVD Media
■ DVD DVD’s are constructed of two half-thickness discs bonded
together,even when only one surface contains information.Each half
disc contains the information layer 0.6 Millimeter (mm) from the sur-
face of the disc.
DVD media consists of two half-thickness polycarbonate discs,each half
containing information and constructed similarly to CD media.DVD write-
once recordable media uses a dye layer with slightly different dyes than those
used for CD-R media,but otherwise are very similar physically.Manufactured
DVD media has the information manufactured into the reflector and no dye
layer is present.Rewritable DVD media uses bi-stable alloy layers similar to
those for CD rewritable media.The differences between manufactured,write-
once,and rewritable media are physically similar between CD and DVD media.
The key to all recordable media types is the presence of a reflector with
the ability to reflect laser energy.Data is represented by blocking the path to
the reflector either by dye or a bi-stable metallic alloy.
The bottom of a CD is made of a relatively thick piece of polycarbonate
plastic.Alternatively,the top is protected by a thin coat of lacquer.Scratches
on the polycarbonate are out of focus when the disc is read,and minor
scratches are ignored completely.It takes a deep scratch in the polycarbonate
to affect the readability of a disc.However,even a small scratch in the lacquer
can damage the reflector.Scratching the top of a disc can render it unread-
able,which is something to consider the next time you place a disc on your
desk top-down “to protect it.”
A DVD has polycarbonate on both sides;therefore,it is difficult to scratch
the reflector.
CD Features
There are a number of distinct areas on the surface of a CD or DVD.Moving
from the inside to the outside of the disc,the following areas are illustrated in
Figure 1.2:
■ A Spindle hole
■ B Clamping ring
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Physical Characteristics of CD and DVD Media • Chapter 1 5
■ C Stacking ring
■ D Mirror band
■ E Beginning of data area
■ F End of data area,slightly inside the outer edge of the disc
The CD standard has specific measurements for all of these areas;approxi-
mately 99 percent of CDs (manufactured or recordable) meet these standards.
DVD measurements are similar to those for CDs and are considered identical.
Figure 1.2 Areas on a CD or DVD
The stacking ring is used to keep the surfaces of discs separate when
stacked on a spindle.Without the stacking ring,the lacquer surface of one
disc would adhere to the polycarbonate surface of the one above it.This is
especially true in high humidity environments.The stacking ring and proper
alignment of stacked discs is important for transporting discs.
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