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International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
6
Survey on Mobile Forensics
Ritika Lohiya
Institute of Technology
Nirma University
Ahmedabad
Priya John
Institute of Technology
Nirma University
Ahmedabad
Pooja Shah
Prof., Institute of Technology
Nirma University
Ahmedabad
ABSTRACT
With the continued growth of smart phone market, the
probability of their use in criminal activities has continued to
increase. Mobile phone nowadays comes with a wide variety
of software application, new technologies and operating
systems. Therefore it becomes complicated for a forensic
investigator to examine the evidence from a mobile phone. A
proper knowledge of forensic tools and their features is
required to collect relevant information. This paper discusses
about the mobile device characteristics, the steps for mobile
forensic investigation and different tools for mobile forensics.
The last section of the paper presents the experimental results
of the tools Mobiledit Lite and Autopsy 3.1.2.
General Terms
Mobile Forensics, Digital Forensics, Forensic Investigation,
Smart phones
Keywords
Mobile Forensics, Forensic Tools, Forensic Investigation.
1. INTRODUCTION
In essence, Forensic Science is often referred to as gathering
and examining the information of an event or a crime. With
the technological advancement, forensic science has evolved
to a great extent. Forensic investigation processes often relay
on the evidence collected by the officials and these evidences
are often in the digital form. And this process of analysing the
digital information for investigation is known as digital
forensics. According to National Security Database (NSD),
digital forensics is a branch of forensic science which deals
with the retrieval and investigation of material found in digital
devices.
Earlier digital forensics was often used to describe the process
of forensic investigation of the crimes which are mostly
related to computer. Digital forensics was used to describe the
crime in which either the computer has been used as a weapon
to conduct the criminal activities or computer has been the
victim of the crime. But nowadays digital device is not limited
to ‘computer’. Today digital device includes computer,
mobile phones, tablet or any electronic device. Forensic
investigation process does not depend on the type of digital
device used, rather the process of investigation is the same for
all kind of digital devices. The investigation process mainly
has three phases: data acquisition which includes acquiring
the data from the device if it is in the sound condition and in
damaged condition the mirror image of the device is produced
which is the used for data retrieval. The next phase is analysis
in which the data acquired is analysed for evidence gathering.
And the last phase is preservation which includes keeping the
data and the evidence collected in safe condition which
further could be used for the presentation of evidence in the
court of law.
Digital forensic is a discipline which includes computer
forensics, mobile forensics and network forensics. The scope
of this paper is to focus on ‘Mobile Forensics’.
Mobile forensics is a branch of digital forensics which
concerns with retrieving the data from a mobile device under
forensically sound conditions. The revolution in mobile
forensics is completely due to the invention of the smart
phones which are equipped with the complete operating
system, software applications and look and feel which make
the interaction with the user easy and comfortable.
Mobile forensics consists of the methods which describes how
to take evidence from the mobile phones and how to analyse
them for information retrieval. It consists of analysis of SIM
and the phone memory. Mobile phone are capable of storing
information just like we store it on our computers and
therefore recovering the deleted information from a phone is
as similar as to recover it from a hard disk.
The best example of mobile phone used as a terror weapon to
execute the crime is the Mumbai terrorist attack in 2008. The
terrorist took the full advantage of being a part of the mobile
phone generation. They connected electronically to each other
as well as their controllers during every phase of their
operation. This attack is not the first time where mobile phone
is used, but the way it was executed is significant and
revealing. In such cases there is a large amount of data that
can be extracted from these devices and used as forensic
evidence.
2. MOBILE DEVICE
CHARACTERISTICS
Mobile phones are capable of executing multiple tasks
ranging from a simple call to storing and preserving data just
like a personal computer. They are mobile, compact in size,
with well powered battery and are light in weight. The basic
set of features include a house of microprocessor, read only
memory (ROM), random access memory (RAM),
microphone, speaker, digital signal processor, a number of
hardware keys and interfaces and liquid crystal display
(LCD). The NAND or NOR memory of the mobile device
consists of the operating system while the code execution
occurs in RAM.
Mobile devices consist of system level microprocessors which
provide the considerable internal memory and also reduce the
number of supporting chips required. Mobile phones consist
of different physical characteristics such as size, memory
International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
7
capacity, processor, speed etc. Also nowadays smart phones
come with many facilities like Global Positioning Systems
(GPS) which is used for navigation and location finding,
cameras which are capable of capturing still images as well as
video recording, office suite which is capable of storing files
and documents just like a personal computer. Earlier mobile
phones were much simpler which were basically used for
simple voice and messaging communications. There were no
facilities as provided by the smart phones and therefore the
mobile devices with such simple look and feel were often
referred to as featured mobile phones.
Below are two tables which differentiate between the featured
phone and a smart phone by classifying them on the basis of
the hardware and software characteristics.
Table 1. Hardware Characteristics of Mobile Device
Category
Feature Phone
Smart Phone
Processor
Speed is Limited
Speed is superior
to the featured
phone.
Memory
Memory is
Limited
Memory is
superior to that of
a featured phone.
Display
Small size colour
display (12 bit-18
bit)
Large size colour
display (approx
24 bit)
Card Slots
None
MiniSDXC
Camera
Still
Still and Video
(HD)
Text Input
Numeric Keypad
Touch Screen,
Built-in
QWERTY keypad
Voice Input
None
Voice
Recognition
(Dialing and
Control)
Positioning
None
GPS receiver
Wireless
IrDA, Bluetooth
Bluetooth, WiFi
and NFC
Mobile phones have a number of software applications and
these applications have a set of features. The table below
describes the software characteristics of the mobile devices.
Table 2: Software Characteristics of Mobile Device
Category
Feature Phone
Smart Phone
Operating
System
Closed
Andriod,
BlackBerry,
Windows, iOS
Personal
Information
Management
Phonebook,
Calender and
Reminder List
Enhanced
Phonebook,
Calender and
Reminder List
Applications
Games, notepad
etc
Games, office
suite, social
media, music etc
Call
Voice
Voice and Video
Messaging
Text messaging
Full multimedia
messaging
Email
Via text
messaging
Via POP or
IMAP server
Web
Via WAP
gateway
Direct HTTP
3. MOBILE DEVICE OPERATING
SYSTEM
The first thing to be investigated while examining a mobile
phone as evidence is whether its Operating System is
compatible with the forensic tool being used by the forensic
scientist. There are two types of Operating Systems - Open
Source and Proprietary.
Android OS: The Android OS is based on Linux 2.6 kernel
that acts like an intermediary between the hardware and the
remaining hardware stack. The Linux kernel is responsible for
provision of services such as process management, memory
management, Inter Process Communication, network protocol
stack, drivers, and security. The framework used in Android
follows object-oriented approach and allows reuse of existing
System, Java and C/C++ libraries. Dalvik VM is a Java virtual
machine (VM) that is designed in such a way that it utilizes
limited system resources during execution. (Source:
http://www.cseweb.ucsd.edu/classes/fa10/cse120/lectures/CS
E120-lecture.pdf)
iOS: The iOS is based on UNIX Operating Systems and
derived from Mac OS X operating system. The foundation
framework is responsible for providing services such as file
management and network management. Using the framework
and Objective C Language, applications are created and
executed on the iPhone directly on the iOS itself. The core OS
layer provides services such as peer to peer connectivity,
security, authentication, concurrency, I/O management,
supports for networking and digital signal processing.
(Source:
https://developer.apple.com/library/ios/documentation/Miscel
laneous/Conceptual/iphoneostechoverview/iOSTechOverview.
pdf)
Blackberry OS: The Blackberry OS [10] is a proprietary
system. It was developed for corporate professional to stay
connected even while travelling. The major APIs such as
memos, calendars, and Java applications access the Research
in Motion (RIM) Java Virtual Machine (JVM). Its functioning
is similar to Android which also relies on Java Virtual
Machine. Mobile Data Service (MDS) deals with internet
related tasks like push mail, instant messaging and file
sharing.
Windows Phone: The Windows Phone is derived from
Windows OS. The essential components of the OS such as the
kernel, graphics support, networking support, file
management and media file handling is managed by the core
OS layer. At a lower level, the OS components of Windows
Phone 8 and Windows 8 are the same. In case of sudden
power failure, data recovery is possible by analyzing the
Transaction- Safe FAT file. NAND and NOR are the two
types of flash memory used in Windows Phone. (Source:
www.cl.cam.ac.uk/~acr31/p36/WP8%20Development%20Ca
mbridge.pdf)
International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
8
Symbian OS: The Symbian OS Core is responsible for
abstraction of the hardware layer. Kernel, Memory
management, Event management and drivers have the same
Symbian OS core. Services for communication like TCP/IP
and SMS are implemented at the System Layer i.e. top of the
Symbian OS core. Since object oriented design is used in
Symbian OS, components or hardware can be added /
removed. The basis of Symbian OS lies on agreed open
standards. Symbian OS is written in C++ language for
efficient utilization of hardware resources and limited
memory constraints. (Source:
http://itu.dk/courses/ISOM/E2005/Nokia_and_Symbian_OS%
5B1%5D.pdf)
4. MOBILE FORENSICS
INVESTIGATION PROCESS
Though there is a very small line of difference between the
computer system and a mobile device but the tools used for
the mobile forensic are totally different. For instance most of
the operating system of the mobile phones is open like
Android but in a feature phone it is closed. And it becomes
difficult to understand the file system and structure of such
phones.
There are diverse forensic tools available for the examination
and analysis of mobile device. Some of them are commercial
and open forensic tools and some non-forensic tools which are
mainly used for device management, testing and diagnostics.
The main aim behind designing these tools was to acquire
data from the internal memory of mobile phones.
Before understanding the various steps in mobile forensic
investigation, we will first discuss about the tool classification
system which is based on the type of data extraction methods
used. It has five levels from Level 1 to Level 5 and as the
level of data extraction increase from bottom to top the
methods involved becomes more technical, invasive, tedious
and expensive.
4.1 Tool Classification System
Manual Extraction
This method refers to acquiring the data from the mobile
device. The content can be on the LCD display which requires
human intervention to operate the keyboard or the touch
screen to get the information. Manual extraction become
difficult when the touch screen is damaged or the keyboard is
missing. Also it is difficult to retrieve data if it is deleted. And
if the device are configured with the languages not known to
the examiner and it becomes difficult to navigate the menu.
Logical Extraction
This method is accomplished by either using wired connection
like a USB or wireless connection like IrDA, WiFi or
Bluetooth. The investigator should know the issues related to
the specific connectivity method as different connection types,
deal with data in a different way. For instance all the
connection types have a protocol associated with it and these
protocols deals with data extraction in a different way.
Logical extraction consists of series of commands which are
exchanged over an interface set between the computer and the
mobile device.
Physical Extraction
This method deals with the raw information stored in the flash
memory of the mobile device. It provides direct access to the
forensic investigator to this information. The most promising
part of this method is the ability of the tool to parse and
decode the captured image and make this information
available to the examiner with the logical view of the file
system. Many techniques are available to physically extract
an image from the mobile device. One of the techniques is to
upload a modified boot loader or some similar kind of
software into the RAM and capture the flash memory and
send it to the forensic workstation. Another method is the
Joint Test Action Group (JTAG). In this technique the
microprocessor of the mobile device is accessed to produce an
image.
Chip-Off
Chip off requires physical removal of the flash memory for
the acquisition of the data directly from the mobile phone.
After extracting the data from the flash memory, examiners
create a binary image of the removed chip. Here in order to
create a binary image of the chip, reverse engineering is
performed on the wear levelling algorithm. After all this is
finished, then data is analyzed for the information gathering.
The biggest challenge of chip-off is that, it requires extensive
training to successfully perform the extraction.
Micro Read
This method requires recording the physical observation of
the gates (NAND or NOR) on the chip by using electron
microscope. It requires an extreme level of technicalities and
so it is used only for high profile cases equivalent to national
security crisis.
4.2 Investigation Steps
Preservation
This is the first and the basic step that provides an insight of
how to deal with the mobile devices. It mainly consists of
searching for the information, recognizing the evidence traits,
documenting the data found and collecting electronically
based evidences. It is very important to preserve data so as to
ensure that it is successfully presented in the court of law.
There are three basic steps involved:
Securing and Evaluating the Scene: This step ensures that the
mobile device found is with proper authorizations for
beginning the investigation. If the device is not handled
properly then it may cause data loss. Also other biometric
investigation procedure like fingerprinting or DNA tests are
carried to establish the link between the device and owner, so
if the device is not handled properly physical evidence may
also get contaminated.
Documenting the Scene: Documenting includes keeping the
record of all the visible data on the mobile device. This is
done mainly for the non-electronic evidence such as invoices,
manuals and packaging material. This provides useful
information like capabilities of the device, the network used,
account information and PIN codes.
Isolation: Isolating the mobile devices from the other devices
used for data synchronization is important to keep new data
from contaminating existing data. For instance if the mobile
phone is found in water and then if it is connected with a
personal computer then pulling a plug from the computer
overwrites the data or the data is lost.
Acquisition
This is the process of cloning the device or generating its
mirror image in order to collect the information from mobile
device. Acquisition has an added advantage that it saves the
loss of information due to battery depletion, damage etc. This
International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
9
step begins with identification of mobile device, the type of
operating system, device characteristics, the interface the
device is using and device label.
Examination and Analysis
Examination process reveals the hidden or the obscured data
of the digital evidence. It takes the copy of the evidence which
is acquired from the mobile device. It also reduces the data by
separating the relevant information from the irrelevant.
Mobile phone manufacturers provide a set of features to
identify the type of data while gathering the information. The
features are like Personal Information Management (PIM),
applications, messaging, e-mail and browsing. With the help
of these features set potential evidence could be obtained
which further may help in the investigation process like:
Date/time, language, and other settings
Phonebook/Contact information
Calendar information
Text messages
Outgoing, incoming, and missed call logs
Electronic mail
Photos
Audio and video recordings
Multi-media messages
Instant messaging
Web browsing activities
Electronic documents
Social media related data
Application related data
Location information
Geo location data
Subscriber and equipment identifiers
Reporting
Lastly, reporting is the process of preparing a document which
summarizes all the steps carried out during the investigation
process. It depends on maintaining a careful record of all
actions and observations describing the results and
examinations and explaining the inferences drawn from the
evidence. A good report relies on the solid documentation,
notes, photographs and tool generated content.
5. MOBILE FORENSICS TOOLS
The number of mobile handsets are increasing day by day.
What further complicates the forensics investigation process
is change in technology. The tools being used by forensic
experts may not be compatible with the latest mobile device
and developing a new forensic tool becomes a challenge. It
becomes necessary to constantly update the database of the
devices supported by the forensic software. The following are
a list of mobile forensics tools:
Table 3. List of Mobile Forensic Tools
Mobile Forensics Tools
(Commercial)
Mobiledit Forensic
iXAM
MSAB XRY
CellDEK TEK
Oxygen Forensic
Paraben DDS
Cellebrite UFED
Mobile Forensics Tools
(Free)
Mobiledit Lite
Bitpim
Autopsy
The results explained in the next section are obtained from
Mobiledit Lite and Autopsy for the device Nokia E71 with
Symbian OS as the operating system. Bitpim has not been
discussed as the enlisted device is not supported by it.
6. EXPERIMENTAL RESULTS
6.1 Mobiledit Lite 7.8.2.6050
Figure 1. Device Information in Mobiledit Lite
Mobiledit Lite is an open source tool for mobile forensics
using which address book, SMS, Media files, Notes and Files
can be analysed. Backup of the phone can be created so that
further analysis is not carried out on the evidence itself. The
software is able to identify the IMEI (International Mobile
Equipment Identity) number of the mobile phone. It has been
blacked out in the image for security purposes. These are the
features provided by the free version.
Additional facilites for authentication bypass, Backup
encryption, Cloning SIM Card and retrieval of Application
data are provided in the commercial tool. (Source:
http://www.mobiledit.com/forensic)
6.2 Autopsy 3.1.2
Autopsy is an open source digital forensic tool that can be
used for investigating cyber-crime. The purpose of the tool is
to identify all possible pieces of information which could be
useful for further forensic examination. Case management,
integrity of disk image, search, time-line analysis are some of
the major functionalities of this tool.
Using Autopsy, mobile phones can be examined for retrieval
of SMS, Contacts, Media files, Calendar and Notes.
Figure 2. Configuration of Ingest modules
International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
10
Multiple ingest modules are executed simultaneously for
better utilization of multi core systems. (Source:
http://www.sleuthkit.org/autopsy/fast.php) The reports can be
generated by the user in HTML, XLS and Body file format.
The report contains the following:
1. Information regarding File Systems (File attributes such as
extension, is deleted, last accessed, last modified, hash value)
2. Information regarding Web Activities (History, Cookies,
Web Search and Downloads)
3. Miscellaneous types (SMS, Location, Call logs, Contacts
and Media files)
This report can be used in documenting evidence related
information or supporting evidence. Detailed analysis of the
files is also possible. The use of Autopsy can be accompanied
with the Sleuth Kit for additional functionalities.
6.3 Case Study
These results have been obtained for Nokia E71 device using
the tool Autopsy to gain more information regarding deleted
file systems. We have recovered the contents of a deleted
Microsoft PowerPoint file. The file type has been correctly
identified as pptx. Each artifact is assigned a unique identifier.
For the PowerPoint File Seminar.pptx, we have obtained the
date and time when it was created, last accessed and modified.
The MD5 value for the file has also been calculated to avoid
any integrity conflicts.
Figure 4. Metadata of deleted file
The Timeline Analysis shows the files accessed during the
given timeframe. This is useful for event reconstruction
during forensics investigation. From timeline analysis, we can
obtain a graphical output of the types of resources present in
the mobile device in the form of documents or media files
with respect to time. The timeline analysis displays the events
occurred in a particular time frame. This helps not only in
identifying suspicious/anomalous activities, but also the time
range in which the incident or event occurred.
6.4 Comparison of Open Source Mobile
Forensic Tools
The following is a comparison table of features of the two
mobile forensics tools discussed. Depending on the type of
evidence to be extracted and analyzed, the appropriate tool
can be chosen.
Table 4. Comparison of Open Source Mobile Forensics
Tools
Parameter
Mobiledit
Autopsy
Operating
System
platform
Windows XP/
2003/ Vista/
Windows7
Windows, Linux
and OSX
Supported
device
Iphone (iOS 3.0 or
higher)
Android
Symbian
Windows (Limited
to contacts and
media files)
Disk images
Local drive,
Folder/ Directory
Connection
via
USB Cable,
WiFi,
Bluetooth,
Infrared
USB Cable
IMEI
Number
Yes
No
Physical
Data
Acquisition
No
Yes
Logical
Data
Acquisition
Yes
Yes
Type of
evidence
recovered
SMS, Contacts,
Files, Media
SMS, Contacts,
Files, Media,
Metadata
Output
format
-
Text, XLS, HTML
Figure 3. List of files
International Journal of Computer Applications (0975 – 8887)
Volume 118 – No.16, May 2015
11
Figure 5. Timeline Analysis
7. CONCLUSION
With the help of open source digital forensic tools like
Mobiledit Lite and Autopsy 3.1.2, details such as SMS, Call
registers, Images, Songs, Videos and Files can be stored for
further investigation. Mobiledit Lite comes with write blocker
(read only) feature so as to ensure the integrity of the mobile
phone is maintained and the evidence is not contaminated.
Mobiledit Lite and Autopsy 3.1.2 alone are not sufficient to
recover deleted items. Other open source tools or commercial
tools can be used along with them for additional functions
such as authentication bypass, SIM cloning and Retrieval of
browsing internet data. Using Timeline Analysis report of
Autopsy 3.1.2, the sequence of events can be established and
useful in event reconstruction.
8. ACKNOWLEDGMENTS
This paper was taken as part of study for forensic science
investigation and Mobile Forensics. We would like to express
our sincere thanks to HOD and guide in Computer Science
Engineering Department, Institute of Technology, Nirma
University for many fruitful discussions and constructive
suggestions throughout.
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