The explosive growth of IT infrastructures, cloud systems, and Internet of Things (IoT) have resulted in complex systems that are extremely difficult to secure and protect against cyberattacks that are growing exponentially in the complexity and also in the number. Overcoming the cybersecurity challenges require cybersecurity environments supporting the development of innovative cybersecurity algorithms and evaluation of the experiments. In this paper, we present the design, analysis, and evaluation of the Cybersecurity Lab as a Service (CLaaS) which offers virtual cybersecurity experiments as a cloud service that can be accessed from anywhere and from any device (desktop, laptop, tablet, smart mobile device, etc.) with Internet connectivity. We exploit cloud computing systems and virtualization technologies to provide isolated and virtual cybersecurity experiments for vulnerability exploitation, launching cyberattacks, how cyber resources and services can be hardened, etc. We also present our performance evaluation and effectiveness of CLaaS experiments used by students.