Along with the transition to the information society, the concept of “cyberspace” became an established term, and it has been defined in various ways in recent years, most of the definitions have focused on the fact that it is an imaginary, virtual environment, in which the electromagnetic activity specific to the informational and information networks of an electronic type, comprising of communication activities, control and command, storage, processing of electronic data, etc., takes place. In a some what narrower sense related to military literature, cyberspace is strictly related to cyber activity, this being intended exclusively for electronic control and command operations, in real or simulated operations. In the common language, cyberspace is not limited in this way, however it is described by all of the activities carried out in the electronic communications networks, regardless of their specific activity. In terms of security, cyberspace has become more and more important as most of the activities of critical importance (these corresponding to the permanent critical infrastructure) are carried out online and depend on electronic databases. With this, the techniques of cyber-aggression have also been developed. Of these, the most well-known and applied ones are those that involve designing and introducing in the cybernetic environment such programs as to cause serious damages, such as unauthorized access and theft, deletion or alteration of data and information, blocking of applications, etc. However, there is also another (much less known and studied) means of carrying out cyber-aggression, namely by using online networks in order to subject their users to harmful electromagnetic emissions, most often through subliminal level effects. This paper will deal with this kind of aggression.