As the historically isolated industrial control systems become increasingly connected, the threat posed by cyberattacks soars. To remedy this issue, industrial standards dedicated to the cybersecurity of ICS have been developed in the last twenty years, namely the IEC 62443 series. These standards provide guidelines to the creation and maintenance of a secure ICS, from the concept phase to its eventual disposal. This standard notably assume a specific Zone/Conduit model for systems, as a basis for building the security program. This model currently lacks computer-aided design tools, which are essential to the adoption of a standard. In this paper, we will present a domain specific modeling language, able to describe IEC 62443 compliant systems. Our main contributions are the DSL's syntax, which tries to formalize the informal model found in the standard, and the validation rules applied to it that ensure the described installations are secure by design, according to a set of hypotheses.