TCP/IP is the standard set of protocols used in Internet communication. Our purpose in this chapter is not to write an exhaustive catalog of TCP/IP security. Rather, we lay the foundation for discussing more advanced topics later in the book, including operating system fingerprinting (Chapter 8) and intrusion detection systems (Chapter 19). In this chapter, we also briefly review attacks on and defense of TCP/IP, including fragmentation attacks and covert channels, and we examine emerging security and privacy issues with IPv6.
The Internet protocols, which are generally implemented on free, open source software, form the standard upon which Internet communication is based. The Transmission Control Protocol (TCP) and Internet Protocol (IP) are the two most important protocols for network security; we focus mainly on these in this chapter, although we also touch on several others.
The protocols were developed in the mid-1970s, when the Defense Advanced Research Projects Agency (DARPA) was working on a packet-switched network to enable communication between disparate computer systems at remote research institutions. TCP/IP was later integrated with Unix, and it has since grown into one of the fundamental communication standards of the Internet. The suggested readings at the end of this chapter reference some of the most relevant de facto standards documents (RFCs).
A TCP/IP packet is simply a package of data. Just like ...