1. Scientific Overview
With the phenomenal growth of the Internet, more and more people enjoy and depend on the
convenience of its provided services. The Internet has spread rapidly almost all over the
world. Up to December 2006, the Internet had been distributed to over 233 countries and
world regions and had more than 1.09 billion users [1]. Unfortunately, the wide use of
computers and the Internet also opens doors to cyber attackers. There are different kinds of
attacks that an end user of a computer or the Internet can meet. For instance, there may be
various viruses on a hard disk, several backdoors open in an operating system, or a lot of
phishing emails in an emailbox. According to the annual Computer Crime Report of the
Computer Security Institute (CSI) and the U.S. Federal Bureau of Investigation (FBI),
released in 2006, cyber attacks cause massive money losses each year.
However, the FBI/CSI survey results also showed that a low percentage of cyber crime cases
have been reported to law enforcement (in 1996, only 16%; in 2006, 25%), which means
that in reality, the vast majority of cyber criminals are never caught or prosecuted. Readers
may ask why this continues to happen. Several factors contribute to this fact:
• In many cases, businesses are often reluctant to report and publicly discuss cyber
crimes related to them. The concern of negative publicity becomes the number-one
reason because it may attract other cyber attackers; undermine the confidence of
customers, suppliers, and investors; and invite the ridicule of competitors.
• Generally, it is much harder to detect cyber crimes than crimes in the physical world.
There are various antiforensics techniques that can help cyber criminals evade
detection, such as information-hiding techniques (steganography, covert channels),
anonymity proxies, stepping stones, and botnets. Even more challenging, cyber
criminals are often insiders or employees of the organizations themselves.
• Attackers may walk across the boundaries of multiple organizations and even
countries. To date, the lack of effective solutions has significantly hindered efforts to
investigate and stop the rapidly growing cyber criminal activities. It is therefore
crucial to develop a forensically sound and efficient solution to track and capture
these criminals.
Here we discuss the basic principles and some specific forensic techniques in attributing real
cyber criminals.
2. The Principles of Network Forensics
Network forensics can be generally defined as a science of discovering and retrieving
evidential information in a networked environment about a crime in such a way as to make
it admissible in court. Different from intrusion detection, all the techniques used for the
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