High Power Microwaves (HPM) is a brutal form of electronic warfare. It relies on that an electromagnetic source can generate enough electromagnetic energy to penetrate into electronic circuits in equipment to disturb or destroy the electronics. This report highlights important results, knowledge and experiences which have been gained during the three year long project "HPM-skyddsmetoder för NBF". The report does also contain a list of the written documentation, and information of how competence has been transferred to other parts of the society, mainly authorities and industry. A general model of how electromagnetic energy hits electronics has been developed. When HPM penetrates through antennas typically a low noise amplifier is destroyed. The susceptibility of these has been investigated. Protection circuits have been developed and investigated. Unintentional penetration through backdoors is hard to characterize. An essential tool in doing so is to use the Reverberation Chamber. Understanding and methods to use the Reverberation Chamber has been developed.