The Ubuntu operating system must be configured to prohibit or restrict the use of functions, ports, protocols, and/or services, as defined in the Ports, Protocols, and Services Management (PPSM) Category Assignments List (CAL) and vulnerability assessments.

From Canonical Ubuntu 16.04 Security Technical Implementation Guide

Associated with: CCI-000382

SV-90489r2_rule The Ubuntu operating system must be configured to prohibit or restrict the use of functions, ports, protocols, and/or services, as defined in the Ports, Protocols, and Services Management (PPSM) Category Assignments List (CAL) and vulnerability assessments.

Vulnerability discussion

In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems.Ubuntu operating systems are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., VPN and IPS); however, doing so increases risk over limiting the services provided by any one component.To support the requirements and principles of least functionality, the Ubuntu operating system must support the organizational requirements, providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues.

Check content

Verify the Uncomplicated Firewall is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems. Check the Uncomplicated Firewall configuration with the following command: # sudo ufw status Status: active To Action From -- ------ ---- [ 1] 22 LIMIT IN Anywhere If any services, ports, or applications are "allowed" and are not documented with the organization, this is a finding.

Fix text

Add/Modify the Ubuntu operating system's firewall settings and/or running services to comply with the Ports, Protocols, and Services Management (PPSM) Category Assignments List (CAL).

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