3.4.9Control what users install in Rev. 3

Organizations employ the principle of least privilege for specific duties and authorized access for users and system processes. Least privilege is applied to the development, implementation, and operation of the system. Organizations consider creating additional processes, roles, and system accounts to achieve least privilege. Security functions include establishing system accounts and assigning privileges, installing software, configuring access authorizations, configuring settings for events to be audited, establishing vulnerability scanning parameters, establishing intrusion detection parameters, and managing audit information. Security-relevant information includes threat and vulnerability information, filtering rules for routers or firewalls, configuration parameters for security services, security architecture, cryptographic key management information, access control lists, and audit information.

Privileged accounts refer to accounts that are granted elevated privileges to access resources (including security functions or security-relevant information) that are otherwise restricted for non-privileged accounts. These accounts are typically described as system administrator or super user accounts. For example, a privileged account is often required in order to perform privileged functions such as executing commands that could modify system behavior. Restricting privileged accounts to specific personnel or roles ensures that only those authorized users can access and manipulate security functions or security-relevant information. Requiring the use of non-privileged accounts when such access is not needed can limit unauthorized access to and manipulation of security functions or security-relevant information.

Privileged functions include establishing system accounts, performing system integrity checks, conducting patching operations, changing system configuration settings, or administering cryptographic key management activities. Non-privileged users do not possess the authorizations to execute privileged functions. Bypassing intrusion detection and prevention mechanisms or malicious code protection mechanisms are examples of privileged functions that require protection from non-privileged users. This requirement represents a condition achieved by the definition of authorized privileges in <a href="#/cprt/framework/version/SP_800_171_3_0_0/home?element=03.01.01">03.01.01</a> and privilege enforcement in <a href="#/cprt/framework/version/SP_800_171_3_0_0/home?element=03.01.02">03.01.02</a>. The misuse of privileged functions — whether intentionally or unintentionally by authorized users or by unauthorized external entities that have compromised system accounts — is a serious and ongoing concern that can have significant adverse impacts on organizations. Logging the use of privileged functions is one way to detect such misuse and mitigate risks from advanced persistent threats and insider threats.

If provided with the necessary privileges, users can install software in organizational systems. To maintain control over the software installed, organizations identify permitted and prohibited actions regarding software installation. Permitted software installations include updates and security patches to existing software and downloading new applications from organization-approved “app stores.” The policies selected for governing user-installed software are organization-developed or provided by some external entity. Policy enforcement methods can include procedural methods and automated methods. Authorized software programs can be limited to specific versions or come from specific sources. To facilitate a comprehensive authorized software process and increase the strength of protection against attacks that bypass application-level authorized software, software programs may be decomposed into and monitored at different levels of detail. These levels include applications, application programming interfaces, application modules, scripts, system processes, system services, kernel functions, registries, drivers, and dynamic link libraries.

Continuous monitoring at the system level facilitates ongoing awareness of the system security posture to support risk management decisions. The terms continuous and ongoing imply that organizations assess and monitor their systems at a frequency that is sufficient to support risk-based decisions. Different types of security requirements may require different monitoring frequencies.