/ FEATURE
BRIEF INTRODUCTION
TO COUNTER-FORENSICS
How Investigators Can Find Themselves Looking for What Isn’t There
by Noemi Kuncik and Andy Harbison Grant Thornton
/ INTERMEDIATE
W
ith the ever-increasing growth of computer performance evidence should be present but is not, rather than detecting the
and storage abilities, together with the expansion of overt use of counter forensic tools. Consequently, investigative
networks and falling costs, digital crime is rapidly be- experience and a thorough grounding in computer science is
coming an everyday worry not only for personal users but also essential in detecting the use of counter-forensics.
for corporations of all sizes. We have seen a considerable upsurge in the use of counter-
Thanks to the sophistication of today’s computers and net- forensics in the last two years, but this has not been refl ected
works, and the spread of knowledge about their workings, digital in the literature. It is our concern that with the proliferation of
criminals can not only carry out their plans and mostly remain electronic discovery, where less attention is typically paid to
anonymous but also cover their tracks. By doing so, they make forensic and ephemeral data, counter-forensics may be under-
it extremely diffi cult and time-consuming for a digital forensic used. We have begun to see sophisticated counter-forensic
investigator to put the pieces together and solve the puzzle. measures being deployed in many of our cases. It has now
In the year 2000, the main focus of digital forensic practitioners become routine procedure for us to check for prior evidence
was probably cyber-crime investigation. Large-scale electronic tampering in every disk we analyse.
discovery did not really come into widespread use until 2003
or 2004, and the large majority of precedent-setting cases date
LARGE-SCALE ELECTRONIC
from 2003 or later. The highly infl uential decisions in Zubulake v
Warburg were made in 2003 - 2005, and the U.S. Federal Rules of DISCOVERY DID NOT REALLY
Civil Procedure were modifi ed to take into account the discovery
COME INTO WIDESPREAD
of electronically stored information in December 2006.
Digital forensic investigation, especially in criminal cases, USE UNTIL 2003 OR 2004
requires a considerable knowledge of computer science.
Nowadays it can be argued that most people working in the There are many possible causes of this upsurge. Public
digital forensic fi eld are electronic discovery practitioners, awareness of digital forensics has greatly increased with its
many of who have insuffi cient knowledge about computers growing use in civil and criminal cases. Most developed coun-
beyond what they see in front of them. Many, perhaps most tries have now seen a number of high-profi le legal cases where
of them are trained on a narrow range of commercial tools. digital forensics techniques have been employed with great
Platform-based certifi cations such as the EnCase Certifi ed success. It is equally possible that the proliferation of police
Examiner (EnCE) are widespread. procedural TV shows in recent years, such as “CSI”, “Forensic
Such training focuses on the correct operation of the soft- Detectives”, and many others (as well as books), have caused
ware in question and the interpretation of the results it dis- this increase in counter-forensic sophistication. These shows
plays. It typically does not consider in detail how computers regularly include examples of digital forensics techniques in use
operate behind the scenes – how they save data and where, and have made people aware of the resources at the disposal
what happens when they are turned on or off, and so on. of investigators, and thus of their own risk of exposure. Another
This can be a handicap when up against advanced computer cause may be simply the growing level of IT understanding
users who deploy sophisticated methods to hide their identi- among the general public in most developed countries.
ties, and cover their tracks by means of counter-forensics. In this article we will give a brief outline of counter-foren-
In most cases misuse, abuse and suspicious activities that sics, and then discuss the different locations where data can
take place inside a computer system can be traced back to their be found in a computer system, and the different types of
perpetrators by an adept digital forensic investigator, However, data present. We will focus mainly on the Microsoft Windows
before such an investigation can even be started the investiga- family of operating systems which are installed on most of
tor needs to be aware that some form of evidence manipula- the world’s computers, especially PCs. Consequently most
tion has occurred. Often this is more a matter of knowing what evidence elimination and counter-forensic tools are oriented
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