From CIA to APT: An Introduction to Cyber Security by Edward G. Amoroso & Matthew E. Amoroso

Author:Edward G. Amoroso & Matthew E. Amoroso
Language: eng
Format: azw3
Published: 2017-08-10T07:00:00+00:00

Figure 14-3. Three-Step TCP Handshake Between Client Browser and Website

This so-called TCP/IP handshake provides the base communication on which most network security methods operate. The most common security method, known as a firewall, sits between clients and servers, and has the obligation to determine what should be allowed and what should be blocked. This is done based on locally defined security policies.

To summarize: The communication plumbing of the Internet is based on the TCP/IP family of protocols. It involves packets being sent between communicating entities, which implies that security protections for the Internet are likely to require integration with these steps of TCP/IP. The initial SYN packet is one of the most important factors in such security integration.

As we will see in the next chapter, policy-based decisions by special security devices called firewalls will depend on many different factors, but one of the most important of these factors is the simple ACK bit in the TCP handshake. That simple bit turns out to play a powerful role in protecting Internet resources from being accessed by unauthorized individuals.

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