In this chapter: Ethical hackers differ from malicious hackers in that ethical hackers seek to do no harm and work to improve an organization's security by thinking like a hacker. This chapter discusses the OSI model and the TCP/IP protocol suite. It looks at some of the most commonly used protocols in the suite and examines how they are used and misused by hackers. Common ports are discussed; as is the principle of deny all. Starting with all ports and protocols blocked leaves the organization in much more of a secure stance than simply blocking ports that are deemed dangerous or unneeded.
Excerpted from Certified Ethical Hacker Exam Prep by Michael Gregg (ISBN: 0789735318).
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