Protected environment assumptions

Cybersecurity governance – available and up-to-date guidance on governing the use of information and technology assets in your company.

Perimeter security – installed devices, and devices that are not in service, are in an access-controlled or monitored location.

Emergency power – the control system provides the capability to switch to and from an emergency power supply without affecting the existing security state or a documented degraded mode.

Firmware upgrades – meter upgrades are implemented consistently to the current version of firmware.

Controls against malware – detection, prevention, and recovery controls to help protect against malware are implemented and combined with appropriate user awareness.

Physical network segmentation – the control system provides the capability to:

• Physically segment control system networks from non-control system networks.

• Physically segment critical control system networks from non-critical control system networks.

Logical isolation of critical networks – the control system provides the capability to logically and physically isolate critical control system networks from non-critical control system networks. For example, using VLANs.

Independence from non-control system networks – the control system provides network services to control system networks, critical or non-critical, without a connection to non-control system networks.

Encrypt protocol transmissions over all external connections using an encrypted tunnel, TLS wrapper or a similar solution.

Zone boundary protection – the control system provides the capability to:

• Manage connections through managed interfaces consisting of appropriate boundary protection devices, such as: proxies, gateways, routers, firewalls, and encrypted tunnels.

• Use an effective architecture, for example, firewalls protecting application gateways residing in a DMZ.

• Control system boundary protections at any designated alternate processing sites should provide the same levels of protection as that of the primary site, for example, data centers.

No public internet connectivity – access from the control system to the internet is not recommended. If a remote site connection is needed, for example, encrypt protocol transmissions.

Resource availability and redundancy – ability to break the connections between different network segments or use duplicate devices in response to an incident.

Manage communication loads – the control system provides the capability to manage communication loads to mitigate the effects of information flooding types of DoS (Denial of Service) events.

Control system backup – available and up-to-date backups for recovery from a control system failure.