Fig. 22: Security zones
Fig. 22 shows three safety zones, but the number of zones is not necessarily decisive, there can
also be more or less - depending on the safety requirement. The use of multiple zones allows
access between zones of different trust levels to be controlled to protect a trusted resource from
attack by a less trusted one.
High-security zones should be kept small and independent. They need to be physically pro-
tected, i.e. physical access to computers, network equipment and network cables must be
limited by physical means to authorized persons only. A high-security zone should obviously not
depend on resources in a less secure zone for its security. Therefore, it should form its own
domain that is administered from the inside, and not depend on, e.g., a domain controller in a
less secure network.
Even if a network zone is regarded as trusted, an attack is still possible: by a user or compro-
mised resource that is inside the trusted zone, or by an outside user or resource that succeeds
to penetrate the secure interconnection. Trust therefore depends also upon the types of meas-
ures taken to detect and prevent compromise of resources and violation of the security policy.
Security for industrial automation and control systems
7.1.2 Secure operation
The controller must be located in a protected environment in order to avoid accidental or
intended access to the controller or the application.
A protected environment can be:
● Locked control cabinets without connection from outside
● No direct internet connection
● Use firewalls and VPN to separate different networks
● Separate different production areas with different access controls
To increase security, physical access protection measures such as fences, turnstiles, cameras
or card readers can be added.
Follow these rules for the protected environment:
● Keep the trusted network as small as possible and independent from other networks.
● Protect the cross-communication of controllers and the communication between controllers
and field devices via standard communication protocols (fieldbus systems) using appro-
priate measures.
● Protect such networks from unauthorized physical access.
● Use fieldbus systems only in protected environments. They are not protected by additional
measures, such as encryption. Open physical or data access to fieldbus systems and their
components is a serious security risk.
Configuration and programming
Cyber security > Secure operation
2023/03/03
3ADR011074, 1, en_US
76