What are the connections between security zones called?

According to the ISA/IEC 62443 standard, the connections between security zones are called conduits. A conduit is defined as a logical or physical grouping of communication channels connecting two or more zones that share common security requirements. A conduit can be used to control and monitor the data flow between zones, and to apply security measures such as encryption, authentication, filtering, or logging. A conduit can also be used to isolate zones from each other in case of a security breach or incident. A conduit can be implemented using various technologies, such as firewalls, routers, switches, cables, or wireless links. However, these technologies are not synonymous with conduits, as they are only components of a conduit. A firewall, for example, can be used to create multiple conduits between different zones, or to protect a single zone fromexternal threats. Therefore, the other options (firewalls, tunnels, and pathways) are not correct names for the connections between security zones. References:

ISA/IEC 62443-3-2:2016 - Security for industrial automation and control systems - Part 3-2: Security risk assessment and system design1

ISA/IEC 62443-3-3:2013 - Security for industrial automation and control systems - Part 3-3: System security requirements and security levels2

Zones and Conduits | Tofino Industrial Security Solution3

Key Concepts of ISA/IEC 62443: Zones & Security Levels | Dragos4