In the past few chapters, we have discussed a lot of topics related to network security from network identity management to attacks and threats. In this chapter, we are going to cover further vulnerabilities within the Transmission Control Protocol/Internet Protocol (TCP/IP) stack. In the early days, during the creation of protocols and TCP/IP, security was not a concern. Cyber criminals and cyber terrorists wasn't even a thing, and the term hacker referred to a person who was a computer wizard and not what is known today, as a person with malicious intentions who uses a computer system to execute harmful tasks. As time passes and the technology evolves, there are more cyber threats each day.
The former CEO of Cisco Systems once said the following: