PROSA by Prosa Security is a software security tool that models and tests system vulnerability in applications and application layers. It utilizes a Domain-Specific Language (DSL) to represent the logic and critical security areas of systems, covering all aspects relevant to IT security in applications. PROSA applies advanced mathematics for developing security models and optionally tests solutions before deployment, simulating attacks affecting the application layer, including data communication. It aids in security evaluations, developer support, and addresses the complexity of modern solutions with numerous servers and protocols.