Lecture #32: Forensic Duplication

Lecture #32: Forensic Duplication
Dr.Ramchandra Mangrulkar
October 8, 2020
Dr.Ramchandra Mangrulkar Lecture #32: Forensic Duplication October 8, 2020 1 / 19

Forensic Duplication
1 During an incident, a significant amount of data is gathered,
preserved, cataloged, and analyzed.
2 The most comprehensive sources of information is a forensic
image of an affected or suspect computer system.
3 Processes, formats, and tools that are used by the forensic
community to properly duplicate data.
4 A court may find that the best available duplication acceptable
and render it admissible.

Types of Forensic Duplication
A simple duplication consists of making a copy of specific data.
The data may consist of a single file, a group of files, a partition
on a hard drive, an entire hard drive, or other elements of data
storage devices and the information stored on them.
A forensic duplication is an accurate copy of data that is created
with the goal of being admissible as evidence in legal
proceedings. Furthermore, we define forensic duplication as an
image of every accessible bit from the source medium.

Characteristics of Forensic Duplication Tools
ability to image or account for every bit of accessible. data on
the storage medium.
must create a forensic duplicate of the original storage medium.
must handle read errors in a robust and graceful manner.
the process must not make any changes to the original storage
medium.
must generate results that are repeatable and veriﬁable by a
third party.
must generate logs that detail the actions requested and any
errors encountered.

Forensics Image Format
IR teams will create and process three primary types of forensic
images
Complete Disk Image
Partition Image
Logical Image

Complete Disk Image
A “complete disk image” is intended to duplicate every
addressable allocation unit on the storage medium.
includes Host Protected Areas (HPAs) and Drive Conﬁguration
Overlays (DCOs).
complete disk image, the output ﬁle contains every allocation
unit, or sector, accessible to the imaging software.

Overview of the Disk Areas
A service area is a logical area on the hard-drive (residing on the
platters) set aside by hard-drive vendors for internally managing the
drive. These areas are outside the hard-drive’s Logical Block Address
(LBA) space and as such are non-addressable and inaccessible via the
standard ATA commands. The service area contains both code and
data modules, such as defect management modules, SMART data
modules, self-test modules and much more.

Disk Areas
Disk Firmware Area (DPA)
The firmware is composed of a series of modules. Examples are:
SECU (Security System Module), P-List, G-List, T-List, SMART
Attributes, and U-List (Firmware Zone Translator).
The Host Protected Area (HPA)
is used for holding diagnostics and other utilities required by the
manufacturer such as the boot sector, the user addressable
sectors, start of the reserved area, and the code for the boot.
A Device Configuration Overlay (DCO) is similar to the HPA,
but is used by manufacturers to configure drive sizes,
to enable and disable features on the disk.

Case Study

Partition Image
Tools allow you specify an individual partition, or volume, as the
source for an image.
A partition image is a subset of a complete disk image and
contains all of the allocation units from an individual partition
on a drive.
A partition image still aﬀords you the opportunity to perform
low-level analysis and attempt to undelete ﬁles and examine
slack space from that partition.
Because a partition image does not capture all the data on a
drive, it is taken only under special circumstances.

Logical Image
A logical image is less of an “image” and more of a simple copy,
and it’s the type of duplication we referred to previously as a
“simple duplication.”
Both FTK Imager and EnCase have the ability to create
evidence containers for logical ﬁles.

Image Integrity
When a forensic image is created, cryptographic checksums are
generated for two reasons.
First, when the image is taken from a drive that is oﬄine
(static) and preserved, the hash is used to verify and
demonstrate that the forensic image is a true and accurate
representation of the original.
Second, the hash is used to detect if the data was modiﬁed since
the point of time at which the image was created.
The hash is simply used to ensure that the integrity has been
maintained throughout the life of the image.

Traditional Duplication
1
Traditional imaging is performed on static drives (that is, hard
drives that are not part of an active, running system
Hardware Write Blockers
The best way to ensure that the source media is not modified in
any way is to use specialized hardware that prohibits write
commands from reaching the drive controller. A set of these
write blockers should be in every IR team’s kit.
The write blockers are typically protocol bridges that contain
modified firmware or an ASIC designed to intercept a subset of
the protocol’s commands.
1
Incident Response Computer Forensics, Third Edition

Case Study

Image Creation Tools
The most common method to create a forensic duplicate is via
software. The three main tools we use are DC3dd, AccessData’s
FTK Imager, and Guidance Software’s EnCase
dd, DCFLdd, and DC3dd

Live System Duplication
A live system duplication is defined as the creation of an image of
media in a system that is actively running.
the system may be an extremely business-critical system that
cannot be taken down.
Performing a live image will make minor modifications to the
system, but you will be able to get an image.
Be sure to document exactly what you did, including the tool
you used, the procedure you followed, what services may be
running, and the exact dates and times.
If “challenged” , the fact that you modified the system. Such
challenges are more easily refuted if you have the proper
documentation.

Duplication of Enterprise Asset
the evidence that is part of an investigation resides on a very
large RAID, SAN, NAS, or other massive central storage system.
it’s infeasible to make a complete duplicate of the entire original
source due to the sheer volume of data or the complexity of the
storage conﬁguration.
formulate an appropriate plan to create a logical copy of only the
relevant data

Lecture #32: Forensic Duplication

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Lecture #32: Forensic Duplication