ESM - External Security Manager
An External Security Manager (ESM) is a mainframe software product, such as IBM's `RACF` (Resource Access Control Facility), Broadcom's `ACF2`, or Broadcom's `Top Secret`, that provides comprehensive, centralized security services for the z/OS operating system and its associated subsystems. Its primary purpose is to control access to system resources, authenticate users, and enforce security policies across the enterprise. An External Security Manager (ESM) is a software product on z/OS that provides centralized security services for the operating system and its subsystems. It is responsible for authenticating users, authorizing access to resources, and maintaining security policies across the mainframe environment. The ESM acts as the gatekeeper, ensuring that only authorized users can access specific resources or perform designated actions.
Key Characteristics
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- Centralized Security Management: Provides a single point of control for defining, managing, and auditing security policies across the entire z/OS environment.
- Granular Access Control: Allows for highly detailed control over who can access what resources (e.g., read-only access to a specific
data set, execute-only access to aload module, update access to aDB2 table). - User Authentication and Authorization: Verifies the identity of users (authentication) and determines their permitted actions on resources (authorization) based on defined rules.
- Auditing and Logging: Records all security-relevant events, including successful and failed access attempts, policy violations, and administrative actions, crucial for compliance and forensics.
- Integration with z/OS and Subsystems: Deeply integrated with the z/OS kernel and key subsystems like
CICS,DB2,IMS,JES, andTSO, extending security protection to their specific resources. - Policy-Driven Security: Security rules are defined as policies that specify user/group permissions for various resource types, enabling consistent and enforceable security posture.
Use Cases
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- User and Group Management: Creating, modifying, and deleting user IDs and security groups, assigning users to groups, and managing password policies for
TSO,CICS, and batch users. - Resource Protection: Securing critical mainframe resources such as
data sets,VSAM files,PDS/PDSE members,DB2 tables,IMS databases,CICS transactions,JCL procedures, andsystem commands. - Application Security: Defining security for specific application components, such as entry points to
COBOLprograms, sensitive data fields, or specific functions within an application. - Compliance and Reporting: Generating audit reports to demonstrate adherence to regulatory requirements (e.g., PCI DSS, GDPR, SOX) by tracking access to sensitive data and system components.
- Delegated Administration: Allowing specific administrators to manage security for certain applications or departments without granting them full system-wide security privileges.
- User and Group Management: Creating, modifying, and deleting user IDs and security groups, assigning users to groups, and managing password policies for
Related Concepts
An ESM is fundamental to z/OS security, working in conjunction with the operating system's native security interfaces, primarily through the RACROUTE macro. It extends and enhances the basic security provided by z/OS, allowing for enterprise-wide, policy-based control. Subsystems like CICS, DB2, and IMS rely heavily on the ESM to validate user access to their transactions, data, and programs. JCL statements often implicitly trigger ESM checks when accessing protected resources, and COBOL programs interact with data and databases whose access is governed by the ESM.
- Principle of Least Privilege: Grant users and applications only the minimum access rights necessary to perform their job functions, reducing the attack surface.
- Role-Based Access Control (RBAC): Implement security based on roles rather than individual users, simplifying management and ensuring consistent permissions for job functions.
- Regular Auditing and Review: Periodically review security logs, access permissions, and user accounts to identify anomalies, enforce policies, and remove stale access.
- Strong Password Policies: Enforce complex password rules, regular password changes, and account lockout mechanisms to prevent unauthorized access.
- Separation of Duties: Design security policies to ensure that no single individual has control over all critical aspects of a process, mitigating the risk of fraud or error.