Cloud-fog-edge computing especially cloud computing is providing a variety of services in many areas around the world and plays a vital role in cyber-physical-social systems (CPSS). Particularly, virtualization is one of main enabling technologies of cloud computing and realizes the dynamic deployment of computing tasks through the migration of virtual machines (VMs), so how to secure the virtual environment in the cloud is very crucial. The purpose of this paper is to address the issue of malware propagation among VMs under the infrastructure as a service (IaaS) architecture. Firstly, a dynamical propagation model is proposed to explore the important factors affecting the spread of malware, especially the impact of installing antivirus software in VMs. On this basis, a theoretical analysis for this model is investigated by means of differential dynamics, from which it is able to understand the dissemination behavior of malware under an infected cloud environment. Finally, some numerical simulations are conducted to verify the applicability and effectiveness of the proposed model. INDEX TERMS Cloud computing security, virtual environment, malware, propagation model, dynamical behavior.