NET-04.1: Deny Traffic by Default & Allow Traffic by Exception

There is no evidence of a capability to configure firewall and router configurations to deny network traffic by default and allow network traffic by exception (e.g., deny all, permit by exception).

Network Security (NET) efforts are ad hoc and inconsistent. CMM Level 1 control maturity would reasonably expect all, or at least most, the following criteria to exist:

• IT personnel use an informal process to design, build and maintain secure networks for test, development, staging and production environments, including the implementation of appropriate cybersecurity and data protection controls.
• Administrative processes are used to configure boundary devices (e.g., firewalls, routers, etc.) to deny network traffic by default and allow network traffic by exception (e.g., deny all, permit by exception).
• Network monitoring is primarily reactive in nature.

Network Security (NET) efforts are requirements-driven and governed at a local/regional level, but are not consistent across the organization. CMM Level 2 control maturity would reasonably expect all, or at least most, the following criteria to exist:

• Network security management is decentralized (e.g., a localized/regionalized function) and uses non-standardized methods to implement secure, resilient and compliant practices.
• IT/cybersecurity personnel identify cybersecurity and data protection controls that are appropriate to address applicable statutory, regulatory and contractual requirements for network security management.
• IT personnel define secure networking practices to protect the confidentiality, integrity, availability and safety of the organization's technology assets, data and network(s).
• Administrative processes and technologies focus on protecting High Value Assets (HVAs), including environments where sensitive/regulated data is stored, transmitted and processed.
• Administrative processes are used to configure boundary devices (e.g., firewalls, routers, etc.) to deny network traffic by default and allow network traffic by exception (e.g., deny all, permit by exception).
• Network segmentation exists to implement separate network addresses (e.g., different subnets) to connect systems in different security domains (e.g., sensitive/regulated data environments).

Network Security (NET) efforts are standardized across the organization and centrally managed, where technically feasible, to ensure consistency. CMM Level 3 control maturity would reasonably expect all, or at least most, the following criteria to exist:

• A Technology Infrastructure team, or similar function, defines centrally-managed network security controls for implementation across the enterprise.
• Secure engineering principles are used to design and implement network security controls (e.g., industry-recognized secure practices) to enforce the concepts of least privilege and least functionality at the network level.
• IT/cybersecurity architects work with the Technology Infrastructure team to implement a “layered defense” network architecture that provides a defense-in-depth approach for redundancy and risk reduction for network-based security controls, including wired and wireless networking.
• Administrative processes and technologies configure boundary devices (e.g., firewalls, routers, etc.) to deny network traffic by default and allow network traffic by exception (e.g., deny all, permit by exception).
• Technologies automate the Access Control Lists (ACLs) and similar rulesets review process to identify security issues and/ or misconfigurations.
• Network segmentation exists to implement separate network addresses (e.g., different subnets) to connect systems in different security domains (e.g., sensitive/regulated data environments).

Network Security (NET) efforts are metrics driven and provide sufficient management insight (based on a quantitative understanding of process capabilities) to predict optimal performance, ensure continued operations and identify areas for improvement. In addition to CMM Level 3 criteria, CMM Level 4 control maturity would reasonably expect all, or at least most, the following criteria to exist:

• Metrics reporting includes quantitative analysis of Key Performance Indicators (KPIs).
• Metrics reporting includes quantitative analysis of Key Risk Indicators (KRIs).
• Scope of metrics, KPIs and KRIs covers organization-wide cybersecurity and data protection controls, including functions performed by third-parties.
• Organizational leadership maintains a formal process to objectively review and respond to metrics, KPIs and KRIs (e.g., monthly or quarterly review).
• Based on metrics analysis, process improvement recommendations are submitted for review and are handled in accordance with change control processes.
• Both business and technical stakeholders are involved in reviewing and approving proposed changes.

Network Security (NET) efforts are “world-class” capabilities that leverage predictive analysis (e.g., machine learning, AI, etc.). In addition to CMM Level 4 criteria, CMM Level 5 control maturity would reasonably expect all, or at least most, the following criteria to exist:

• Stakeholders make time-sensitive decisions to support operational efficiency, which may include automated remediation actions.
• Based on predictive analysis, process improvements are implemented according to “continuous improvement” practices that affect process changes.