The term "Cyber" is relatively new (first mentioned in the 1970s) and professionals have not reached a consensus on what Cyber means. That being said, the term Cyber is so widely used that most people have a general idea of what it entails. For the purpose of this course we will use the following two definitions when thinking about Cyber:

• Common: In Layman's terms the Cyber domain is "the domain characterized by the 'human' use of electronics and the electromagnetic spectrum to store, modify, and exchange data via networked systems and associated physical infrastructures."

• Department of Defense: The Joint Publication 3-12 on Cyberspace Operations (JP 3-12) defines the Cyber domain as "a global domain within the information environment consisting of the interdependent networks of information technology infrastructures and resident data, including the Internet, telecommunications networks, computer systems, and embedded processors and controllers."

This course uses the extended cyber stack model to describe the space which cyber systems of interest exist. This model is based on teh TCP/IP model, that you may remember from Cyber I. While the TCP/IP model offers a framework for how computers and machines communicate, this course is interested in much more. Not only do we as engineers care about how machines exchange information, we also care how those machines store and manipulate information. The diagram to the left shows this model, which we will use to guide the instruction of this course.