Dependence on computers has had a transformative effect on human society. Cybernetics is now woven into the core functions of virtually every basic institution, including our oldest ones. War is one such institution, and the digital revolution's impact on it has been profound. The Americanmilitary, which has no peer, is almost completely reliant on high-tech computer systems. Given the Internet's potential for full-spectrum surveillance and information disruption, the marshaling of computer networks represents the next stage of cyberwar. Indeed, it is upon us already. The recentStuxnet episode, in which Israel fed a malignant computer virus into Iran's nuclear facilities, is one such example. Penetration into US government computer systems by Chinese hackers - presumably sponsored by the Chinese government - is another. Together, they point to a new era in the evolution ofhuman conflict. In Cybersecurity: What Everyone Needs to Know, noted experts Peter W. Singer and Allan Friedman lay out how the revolution in military cybernetics occurred and explain where it is headed. They begin with an explanation of what cyberspace is before moving on to discussions of how it can be exploitedand why it is so hard to defend. Throughout, they discuss the latest developments in military and security technology. Singer and Friedman close with a discussion of how people and governments can protect themselves. In sum, Cybersecurity is the definitive account on the subject for the educatedlayman who wants to know more about the nature of war, conflict, and security in the twenty first century.