As cyber threats grow increasingly sophisticated, the importance of security training as an effective means of prevention will become even more critical. Cyber Range (CR) is a platform for creating cyber training programs using virtualization and simulation technologies to create a realistic training environment. The main challenge for utilizing a CR is the specialized human resources required to design and maintain training sessions. To tackle this challenge, several high-level languages, known as Scenario Description Languages (SDLs), have been developed to enable the specification of training environments as models. These models can then be automatically transformed into deployment artifacts. Our studies showed that the existing SDLs could not address requirements when designing complex scenarios where multiple trainees should collaborate to reach a desired goal through various acceptable solutions. We present the Collaborative Security Training SDL (CST-SDL) for creating multi-trainee and multi-solution scenarios. CST-SDL uses an acyclic directional graph for specifying the scenario's solution routes and allows defining trainees with unique tasks, goals, and solution routes during the training session. To evaluate the CST-SDL's capabilities, we have implemented and integrated it into the KYPO cyber range.
