Cyber-technology is a new and emerging area of dual use concern. Consider autonomous robots. On the one hand, autonomous robots can provide great benefits, e.g. providing for the health and safety of elderly invalids. On the other hand, autonomous robots have the potential to enable great harm, e.g. weaponised autonomous robots (so-called ‘killer robotsweaponised autonomous robots’). As we have seen, the intended great harm is typically delivered by a weapons system of some sort, e.g. chemical, nuclear or biological weapons. Cyber-technology is apparently no different in this respect since, after all, there are so-called cyber-weapons, such as the Stuxnet virus used to shut down Iranian nuclear facilities. In this chapter the definition of dual use technology elaborated in Chap. 2 is modified in light of some distinctive properties of cyber-technology. This modified definition is applied to cyber-technology with a view to identifying cyber-technologies that are dual use technologies. It is concluded that weaponised autonomous robots, various forms of computer viruses, and ransomware are dual use technologies, but that the internet and other forms of cyber-infrastructure are not.