Security engineering  Security engineering is a specialized field of engineering that focuses on the security aspects in the design of systems that need to be able to deal robustly with possible sources of disruption, ranging from natural disasters to malicious acts. It is similar to other systems engineering activities in that its primary motivation is to support the delivery of engineering solutions that satisfy pre-defined functional and user requirements, but it has the added dimension of preventing misuse and malicious behavior. Those constraints and restrictions are often asserted as a security policy. In one form or another, security engineering has existed as an informal field of study for several centuries. For example, the fields of locksmithing and security printing have been around for many years. Recent catastrophic events, most notably 9/11, have made security engineering quickly become a rapidly-growing field. In fact, in a report completed in 2006, it was estimated that the global security industry was valued at US$150 billion. Security engineering involves aspects of social science, psychology (such as designing a system to "fail well", instead of trying to eliminate all sources of error), and economics as well as physics, chemistry, mathematics, criminology architecture, and landscaping. Some of the techniques used, such as fault tree analysis, are derived from safety engineering. Other techniques such as cryptography were previously restricted to military applications. One of the pioneers of security engineering as a formal field of study is Ross Anderson. No single qualification exists to become a security engineer. However, an undergraduate and/or graduate degree, often in computer science, computer engineering, or physical protection focused degrees such as Security Science, in combination with practical work experience (systems, network engineering, software development, physical protection system modelling etc.) most qualifies an individual to succeed in the field. Other degree qualifications with a security focus exist. Multiple certifications, such as the Certified Information Systems Security Professional, or Certified Physical Security Professional are available that may demonstrate expertise in the field. Regardless of the qualification, the course must include a knowledge base to diagnose the security system drivers, security theory and principles including defense in depth, protection in depth, situational crime prevention and crime prevention through environmental design to set the protection strategy (professional inference), and technical knowledge including physics and mathematics to design and commission the engineering treatment solution. All this knowledge must be braced by professional attributes including strong communication skills and high levels of literacy for engineering report writing. Security engineering also goes by the label Security Science. Technological advances, principally in the field of computers, have now allowed the creation of far more complex systems, with new and complex security problems.