Android forensics

MOBILE SECURITY

Android Forensics
Smartphones are changing the IT and Communication landscape vastly.
A Smartphone can do almost every good thing a computer can do. Today

through the e-mail client installed on their Smartphone.

R
ight from booking movie tickets to making fund • Android device is targeted by the attacker.
transfers, all e-commerce and online banking • Android device is used as a means to carry out
transactions can be done using a Smartphone. cyber crime.
With high speed of 3G, Smartphones are getting more
popular specially among working professionals and Let us consider some of the real world cases. What if
students. an Android device is discovered from a crime location??
As Smartphone market is growing, it is also catching What all evidences can be discovered from the
bad guy’s attentions. For bad guys or hackers, it is device?? Where exactly to look for the evidences??
easy to target mobile users as they are less aware and These are some challenges faced while doing
bother less about the risks associated with the mobile forensic analysis on Android device. First we will see
and mobile applications. what all bad things can be done with the Smartphone
There are number of Mobile Operating Systems (or how a Smartphone can be used in various criminal
present in the market. Among these Mobile OS, Android, activities).
iOS and RIM are more popular than others. Android is
the most widely used Mobile OS present in the market. Cyber Crimes through Smartphones
According to Gartner report, Android had more than 36% Software Theft: Software theft is now a common attack.
share of the market by end of the first quarter of 2011. If codebase of your software is stolen and sold to your
It is quite obvious that the widely used platform is likely rival, he can make a great loss to your company. Your
to be targeted more, as in the case of Microsoft Windows rivals are ready to invest huge money to obtain source
Operating System. A hacker wants to target mass and code of your key software.
for doing that he has to target the most commonly used A Smartphone can carry large volume of sensitive
platform. Android is one such commonly used platform. data. It can be used in carrying codebase of any key
As Android is capturing market, it is becoming favorite software of any company. There are security guards
target platform of hackers. and other mechanism in place to check the employees
It is always a challenge for forensic examiners to and visitors, if they are carrying any business critical
discover the evidences from the Android devices. information in any form. But still they hardly check for
Android has a different and newer file system, Mobile phones.
directory structure, runtime environment, kernel and In one classic case of Software theft, an unhappy
libraries which make Android more complex to forensic employ of a company used to carry all source code of
examiner. We will discuss detailed forensics steps to the key software of the company in her smart phone.
examine Android device in later part of this article. She first copied the code in her phone’s external storage
and then deleted the same data from the phone. When
How Android can be used in Cyber Crime her phone was observed at security check, nothing was
Android can be used in cyber crime in two ways: found in her phone. When she reached home, she used

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Android Forensics

a tool to recover the deleted data. This way she took all really needs to learn something special to analyze
the data out from her company and latterly she sold the Android devices?? Can evidences be discovered from
source code to the rival of her employer. the device?? Are they admissible in the court of law??
Terrorist Activities: Terrorists also use Smartphones Next section of the article will answer all the above
to exchange and store the information. They use questions in further detail.
Smartphones to communicate with the other member
of the terrorist organization. They also use GPS to Forensic Process of Android Device
find locations. They can store various data in the Forensic process of Android phone will comprise of
Smartphone like maps or photos of target locations, following steps:
encrypted and stagno files, instructions etc. They can Seizing Android device: If an Android device or any
use the phone to click photos of target locations. Smartphone is discovered from any crime location, first
Pornography/Child Pornography: Pornography thing a forensic investigator should do is to click the
is fully banned in a number of countries. And child photos of the crime scene including the photo of the
pornography is considered a big offence across the device. If phone is ON, take photo of display as well.
world. Smartphone can be used to store, view, capture If you find mobile to be ON then keep charging the
and exchange such kind of materials. mobile so that the battery does not drain. In case,
Sexual Harassment Cases: Smartphone can play big we don’t charge the phone and the phone goes OFF,
role in sexual harassment kind of cases. If a Smartphone we may lose the important data especially regarding
is discovered from accused, a forensic examiner can current or recent applications. If phone is OFF at the
get treasures of information from the device. time it was recovered, keep it OFF. Seize all other
Financial Crimes: Every other bank is developing available accessories i.e. memory card, data cable etc.
banking and other non-financial application to facilitate As soon as we recover anything, start labeling it. It
their mobile customers. These applications can be is required to maintain and present a chain of custody
used for malicious activities by hackers. A Smartphone at the court of law. A label should have the following
recovered in financial fraud cases can give many minimum information on it:
evidences about the case.
Murder Cases: Even in murder or other criminal cases, • What is the evidence?
a Smartphone can provide evidence useful in solving the • How did you obtain it?
case. Right from call records and SMSes to facebook • When was it collected?
records or GPS data can be recovered from the phone. • Who all have handled it?
Let us think about, what all evidences can be • Why did that person handle it?
recovered from a Smartphone?? Where to look in the • Where has it travelled and where was it ultimately
Smartphone?? We will discuss in coming section that stored?
what all evidences we can discover from a Smartphone: • What is Case ID?

Interesting locations for Forensics Chain of Custody is a chronological documentation of
Investigation individuals who had physical possession of the evidence.
Maintaining the chain of custody is vital and it guarantee
• Phone Browser Memory
• Application storage
• External Card
• SQLite database files
• SMS
• GPS data
• Call records
• Contact list
• Social networking application (Facebook, Twitter,
Orkut) records
• Messenger (Yahoo, MSN) records
• Email client data
• System storage
• Data stored in external card

How investigation of Android device is different than
other Smartphones?? Does forensic investigators Figure 1. Chain of Custody Form

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MOBILE SECURITY
the integrity of the evidence, right from collection to the
final test result. Chain of custody is something must to have
document in any criminal trial. If proper Chain of custody has
not been maintained, court may not consider that evidence
in making final verdict.

Creating 1:1 Image Figure 3. Winhex Making device Write Protected
Creating image is the most important task in any forensic
analysis. It is the thumb rule in forensic investigation One more thing we should take care of before
that you cannot work on primary evidences if you want creating image is to make the target device in write
them to take in the court of law. For that we need to protected mode. Whenever you connect any device to
create bit-by-bit image of the target device. your computer, there are chances that some data can
What is bit-by-bit image and how it is different from be written on the devices by any software, application
the copy-paste the content of entire disk?? or OS. In that case your evidence (device) is no more
If we copy and paste the content of a disk, this will genuine. Just to avoid this kind of situation, make the
only copy visible, hidden and system files. Whatever disk or device write protected. To do that, use write
is deleted or not accessible by the OS would not be protected cables present in the market. In this article,
copied by copy command. So, for a thorough analysis, we will make device write protected by software to
it is required to create a 1:1 image of the disk. Bit-by- explain the technique.
bit image is as good as the original image. Thorough Creating image of external memory card: We will
analysis is not the only reason we need to take 1:1 start with simpler part of imaging, which is creating
image, it is also required by the court of law. If you have image of the memory card. In most of the cases, file
not taken 1:1 image, your evidences are not admissible system of the memory card is FAT32 and it is easy to
in the court of law. image. There are lots of free and commercial tools
How we will take image of an Android device?? available in the market which can help us in creating
How I can verify that my image is exact bit-by-bit copy image of the memory card. We will use free version
of original disk or device?? How can I establish the of Winhex to do that. Winhex is a powerful forensic
authenticity of the image?? tool. It is available in both freeware and commercial
There are two locations to be taken image of in case versions.
of Android device. One is the device and other is the
external card. We will see in following section that how Note
to create a bit-by-bit image of the Android device. But Only commercial tools should be used to discover the
before that we will see how to verify the image. evidences in case you want to take evidences to the
Before starting the imaging of original disk, calculate court.
the hash value of it and note that down. Now after taking Here are the detailed steps to take the 1:1 image of
image, calculate the hash value again for the image. the memory card:
If hash values are same for both the image and disk, First remove the SD card and connect the card to the
we can be sure that we have taken exact image of the computer with any card reader. Now we will make the
original disk. Now we can work on image and evidences device write protected through Winhex. Follow below
discovered from the image can be taken to the court step to do that: Open the disk in Winhex: Figure 2.
along with the hash values calculated. The hash value Go to Options then Edit mode and select first option
establishes the authenticity of the image that it has not write protected mode: Figure 3.
been tampered. Now calculate the hash value for SD card.

Figure 2. Winhex Opening SD Card Figure 4. Winhex Creating Image

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Android Forensics

To calculate hash, go to Tools then Compute hash and the device to get the superuser permission. There are
choose any H ashing a lgorithm. We have t o compare various techniques available in the market that can help
this hash value w ith the hash value computed earlier you in rooting your Android phone. Among them, Odin3
for the image. Now we create the image of the disk. Go software is one such popular tool. All you need to do is
to File menu and click on Create Disk Image option for to check the build number of your phone. You can check
creating an image. Choose Raw image option (.dd) to
create image, as dd image is interpreted by almost all
commercial and open source forensic tools (Figure 4).
Image o f memory card is c reated. W e will use t his
image for analysis in later part of the article.

Creating Image of Android device
This is a tricky part. A ndroid does not p rovide any
direct w ay t o access o r view i ts i nternal d irectories or
system f iles and d irectories. B ut i nternal o r system
locations may have most critical data stored. Almost all
applications write some application data and temporary
data in t hese d irectories only. /data/data i s the most
interesting location for the forensic investigator which is
not accessible to the user. Only application or root users
have access to these locations.
How w e can access A ndroid internal d irectory
structure?? H ow t o create the image o f the Android
internal directory structure??
For this we need to obtain ROOT permission on the
Android OS. In Android terminology, we need to ROOT Figure 5. Kernal Build Number

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MOBILE SECURITY

Figure 6. DD Command Figure 8. Winhex Interpreting Image as Disk
it by visiting the following location in any Android phone: As it is known to all that Android uses Linux kernel
Settings-> About Phone-> Build number. Now Google 2.6. By downloading Terminal Emulator application
for the rooted kernel for this build number and pass all from the Android Market, we can run almost all Linux
the files to Odin3 software. This way you can ROOT commands. So, to create image of device, we will be
your phone. There number of good tutorial available in using dd command. DD stands for Data Description,
the market on Android Rooting. As per my knowledge it does low-level copying of data in Linux. The dd
ROOTING is legal and it does not void any warranty. command will help us in creating bit-by-bit image of
Still check local laws before rooting your phone. I have Android device.
never come across such situations; still it is a general To take backup, insert a fresh SD card in device
belief that rooting may harm your system or you may and copy the target data there. Typical syntax of DD
lose your entire data stored on the phone. command:

Note dd if=/dev/fd0 of=tmp.image
In the rooting process, something will be written on
target device and as I mentioned earlier, we can’t write Where if is input file and of is output file. Again, output
anything on the phone, if we want to take that into of the dd command is understood by all commercial
court of law as evidence. The method and technique and open source forensic tools including WinHex,
explained in this example may not be accepted by the EnCase, Helix, Forensic Toolkit etc.
court. In this case, one can take approval in advance To take the backup of the Android system folders,
from the court. That is again subject to local laws. So go to /proc/mnt file and open the mnt file. You will have
now we have root access on the phone, what next?? similar to following structure:

Figure 7. Winhex Reading Image Figure 9. Winhex Hidden Files and Folders

26 02/2012

Android Forensics

dev: size erasesize name like FTK or EnCase have inbuilt feature of identifying
mtd0: 000a0000 00020000 „misc” and restoring deleted data.
mtd1: 00480000 00020000 „recovery”
mtd2: 00300000 00020000 „boot” Analyzing the Data
mtd3: 0fa00000 00020000 „system” Analyzing Android data is a bit different; one should
mtd4: 02800000 00020000 „cache” know the important locations to be checked out. More
mtd5: 093a0000 00020000 „userdata” manual intelligence is required in this step of forensic
analysis of Android device. For example, in case of
Copy one by one location through DD command. money laundering related cases; email, browser data
To understand the concept, we will be copying some and banking application related data must be looked at
directories with dd command as shown Figure 6. to discover any clue. Same is true in the case of sexual
harassment case; emails, social networking data, SMS
Recovering Data will be interesting locations to search for evidences.
Now we are done with the imaging part. The image For example below file was recovered from Skype
created in above steps can be accepted by any forensic application. I have used same dd command to recover
tool. We will be using free version of Winhex to recover this file. The format for this file was .DAT. I have opened
and analyze the data as well. this file in a text editor (notepad in this case). You can
In most of cases, criminal deletes suspicious
data or even format the entire disk. Suppose in any records; everything in plain text. Same way you can
pornography related case, we hardly find anything in the get useful information from other applications like
device, because all data has been intestinally deleted. Facebook, Yahoo Messenger, Twitter etc. All application
So, before starting analysis part, it is recommended to related data can be found at the following location:
recover all deleted or destroyed data first. /data/data/com.application/; (Figure 10).
To recover deleted data, open the image file in
Winhex. Go to File menu then Open option, select the
image file and click ok. Figure 7 show the opened image SQLite database files are most interesting files for
file. forensic investigators. One will get most critical
As we can see from the above screenshot, all information here, even username and passwords in
data is represented in hex form. To make the data some cases.
understandable, we need to interpret the image as disk. SQLite is a lightweight database (RDBMS) and used
To do that, go to Specialist menu and click on Interpret by almost all Smartphone OS like Android, iOS and
Image File As Disk as shown Figure 8. Blackberry. SQLite files can be found at the following
Folders highlighted in the Figure 9 are the deleted location:
folders.
To recover deleted files or folder, right click on target /data/data/com.application_name/databases
folder and click on Recover/Copy and select location to
save the file. For example we want to see all SQLite files created
There are number of tools available to recover and maintained by Facebook. Then we need to look at
deleted or destroyed data. All well known forensic tools following location for db files:

/data/data/com.facebook.katana/
databses

All SQLite files stored with .db
format. I have copied a few
sample .db files (from Facebook,
email client etc) using dd
command to explain analysis of
SQLite database files.
To understand the concept, I
will be using free version of Epilog
tool. Epilog is a powerful tool for all
kind of SQLite files.
Open a db file in Epilog tool,
Figure 10. Skype File in this example we are opening

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MOBILE SECURITY
with all the useful information like
Contacts, SMSes, IM records etc.
Figure 12 shows the HTML
report from viaExtract tool, we
cans see all SMS details here.

Note
Even viaExtract will write
something on the device.

Reporting Evidences
Reporting has to be done on case to
case basis. There are different ways
of reporting evidences in corporate
cases and criminal cases. Reported
Figure 11.
evidences should be clear, give
direct or indirect reference to the
possible scenarios of crime.
In a criminal case, where we
want to present evidences in the
court of law, it is also required to
map the findings with respective
laws. In addition to evidences, it is
also required to present Chain of
Custody. Again reporting depends
on country to country, as the Cyber
Laws varies with geography.

Conclusion
To summarize, analyzing Android
for forensic purpose employs
Figure 12. viaExtract Report totally different techniques than
the traditional forensics. It involves
fb.db (Facebook db file). Check Do Generic Record heavy manual intelligence and interference. Maintaining
Extraction checkbox and click on process (Figure 11). integrity of primary evidences is also a challenge. There
You can observe in above screenshot, fb.db file contain are tools available in the market for Android Forensics
some really useful information. In our case, we can see but still there are gaps to be filled and a lot to be done in
full names, email ids, phone numbers of the friends added this direction. After learning about forensic process, it will
in Facebook friendlist of the suspect. By opening the
correct db file, we can even find all the chat logs, personal
messages and other details. In some cases, you may even MANISH CHASTA
find username and password stored in a SQLite files.
Analyst, working with Indusface (Mumbai) as
viaExtract Tool Principal Consultant. He is having more than 5.5 years of
There are a number of good forensic tools available in experience in Information and Application security. He is
the market, out of them I found viaExtract tool to be very currently managing team of security engineers and doing
useful and easy to use for Android forensic. This tool is a vast research in Mobile Application Security. He is also
specially meant for Android forensic by viaForensic. handling prime customer accounts for the company. He
In this tool, you just need to connect the phone to the has authored numerous security articles for ClubHack and
machine where viaExtract is installed. Phone should Palisade. He has audited 200+ mobile and web-applications
be in USB debugging mode. To make phone in USB in the areas of Internet Banking, Core Banking (Flexcube),
Debugging mode, go to Settings-> Applications-> Finance, Healthcare, CRM, telecom and eCommerce. He has
Development and select USB Debugging mode. Now
you just need to click Next and tool will recover and Security and Ethical Hacking to multiple clients.
analyze the device. As an output, you get final report Email id: chasta.manish@gmail.com

28 02/2012

Android forensics

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