The current development of drones and the prospects in this field have positive repercussions, in particular for employment and industrial development, with the key to growth and job creation possibilities. Drones have the ability to conduct operations in emergency situations, where human intervention is impossible or difficult. They could help save lives in humanitarian emergencies, nuclear accidents or natural disasters, etc. As with any technology, there are also risks that must be seriously considered by stakeholders, regulators, institutions and citizens, in order to prevent, minimize and avoid possible negative consequences of certain applications of this technology. In fact, drones today also present risks of cybersecurity breaches and malicious use. In this paper, we concentrate on security challenges related to the use of drones. More specifically, we give a short overview of the possible threats, attacks and countermeasures related to drone communications. The considered countermeasures are mainly based on the use of: Blockchain Technology, Machine Learning (ML) Techniques, Fog Computing and Software Defined Networks (SDN).