This unit provides an introduction to the many facets of security in the digital and networked world, the challenges that computer systems face, and the design principles that have been developed to build secure systems and counter attacks. The unit puts the focus squarely on providing a thorough understanding of security principles and engineering for security. At the same time, we stress a hands-on approach to teach the stateof-the-art incarnations of security principles and technology, pretesting, and we practice programming for security. We pay particular attention to the fact that security is much more than just technology as we discuss the fields of usability in security, operational security, and cyberphysical systems. At the end of this unit, graduates are prepared for practical demands in their later careers and know how to tackle new, yet unforeseen challenges.