External Security Manager

ESM

Enhanced Definition

An External Security Manager (ESM) is a software product on z/OS that provides centralized control over system resources, user authentication, and authorization. It enforces security policies across the entire mainframe environment, ensuring that only authorized users can access specific data, programs, and system functions. Prominent examples include IBM's `RACF` (Resource Access Control Facility), Broadcom's `ACF2`, and `Top Secret`.

Key Characteristics

- Centralized Policy Enforcement: Manages security rules and profiles from a single point, simplifying administration and ensuring consistent security across the system.
- Granular Resource Protection: Allows administrators to define access rules at a very detailed level, protecting datasets, programs, CICS transactions, DB2 tables, IMS resources, and more.
- Authentication and Authorization: Verifies user identities (authentication) and determines what resources they are permitted to access (authorization) based on defined rules.
- Auditing and Logging: Records security-relevant events, such as access attempts (successful or failed), policy changes, and user activity, for compliance and forensic analysis.
- Integration with z/OS Components: Deeply integrated with the z/OS operating system, subsystems (CICS, DB2, IMS, MQ), and applications to intercept access requests and apply security rules.
- User and Group Management: Provides facilities to create, modify, and delete user IDs, assign them to groups, and manage their passwords and security attributes.

Use Cases

- Controlling Access to Production Data: Ensuring that only authorized personnel (e.g., specific application teams) can read, update, or delete sensitive production datasets.
- Securing CICS Transactions: Restricting which users can execute specific CICS transactions, preventing unauthorized access to critical business functions.
- Protecting DB2 Tables and Views: Defining granular access controls for specific tables, views, or even columns within a DB2 subsystem.
- Managing JCL Execution Privileges: Controlling which users or groups can submit jobs, execute specific programs via JCL, or access particular JES resources.
- Implementing Multi-Factor Authentication (MFA): Integrating with MFA solutions to add an extra layer of security beyond traditional passwords for user logon.

Related Concepts

An ESM is fundamental to the overall security posture of a z/OS system, working in conjunction with various components. It interacts with the z/OS operating system to intercept SVCs and enforce security decisions. It provides security for subsystems like CICS, DB2, IMS, and MQ by validating access requests made by applications or users within those environments. JCL often includes RACF or ACF2 parameters for job -level security, and the ESM manages the user IDs and groups defined for COBOL or other application programs, ensuring their execution context is properly secured.

Best Practices:

Principle of Least Privilege: Grant users only the minimum access rights necessary to perform their job functions, reducing the risk of unauthorized access.
Regular Auditing and Review: Periodically review security logs and access profiles to identify anomalies, ensure compliance, and remove stale or excessive permissions.
Strong Password Policies: Enforce complex password rules, regular password changes, and account lockout mechanisms to prevent brute-force attacks.
Segregation of Duties (SoD): Implement security policies that prevent a single individual from controlling multiple critical steps in a process, mitigating fraud and error.
Utilize Groups for Permissions: Assign permissions to groups rather than individual users to simplify administration and ensure consistency, especially for application access.