In the context of security, risk analyzes are widely recognized as essential. However, such analyzes need to be replayed frequently to take into account new vulnerabilities, new protections, etc.. As exploits can now easily be found on internet, allowing a wide range of possible intruders with various capacities, motivations and resources. In particular in the case of industrial control systems (also called SCADA) that interact with the physical world, any breach can lead to disasters for humans and the environment. Alongside of classical security properties such as secrecy or authentication, SCADA must ensure safety properties relative to the industrial process they control. In this paper, we propose an approach to assess the security of industrial systems. This approach aims to find applicative attacks taking into account various parameters such as the behavior of the process, the safety properties that must be ensured. We also model the possible positions and capacities of attackers allowing a precise control of these attackers. We instrument our approach using the well known model-checker UPPAAL, we apply it on a case study and show how variations of properties, network topologies, and attacker models can drastically change the obtained results.