IDS - Intrusion Detection System

Enhanced Definition

An Intrusion Detection System (IDS) on IBM z/OS is a security mechanism designed to monitor system activities, network traffic, and audit logs for signs of malicious activity, policy violations, or unauthorized access attempts. Its primary purpose is to identify and alert administrators to potential security breaches or suspicious behavior within the mainframe environment.

Key Characteristics

- Monitoring Scope: Monitors a wide range of z/OS activities, including SMF records (especially SMF type 80 for security events), syslog messages, RACF/ACF2/Top Secret audit trails, CICS logs, DB2 audit logs, and network traffic directed at z/OS.
- Detection Methods: Employs signature-based detection (identifying known attack patterns), anomaly-based detection (flagging deviations from established baselines of normal behavior), and policy-based detection (enforcing defined security rules).
- Passive Nature: Typically operates in a passive mode, focusing on detection and alerting rather than actively preventing or blocking intrusions, which is characteristic of an Intrusion Prevention System (IPS).
- Alerting Mechanisms: Generates alerts through various channels, such as console messages, WTO (Write To Operator) messages, email notifications, SNMP traps, and forwarding events to a Security Information and Event Management (SIEM) system.
- Integration with Security Managers: Relies heavily on the rich audit data generated by z/OS security managers like RACF, ACF2, and Top Secret to provide context and detail for detected events.

Use Cases

- Unauthorized Access Detection: Identifying repeated failed login attempts, attempts to access unauthorized datasets or resources, or privilege escalation attempts by users.
- Compliance Auditing: Providing a critical component for demonstrating compliance with regulatory requirements (e.g., PCI DSS, GDPR, SOX) by continuously monitoring and logging security-relevant events.
- Insider Threat Detection: Monitoring the activities of privileged users or employees for suspicious patterns that might indicate malicious intent or accidental misuse of privileges.
- Malware and Ransomware Indicators: Detecting unusual file access patterns, unauthorized program executions, or changes to critical system files that could indicate a compromise.
- Network Anomaly Detection: Analyzing network connections to and from the z/OS system for unusual traffic volumes, unexpected protocols, or connections from suspicious IP addresses.

Related Concepts

An IDS on z/OS works in conjunction with the system's native security capabilities, particularly the External Security Manager (ESM) like RACF. While the ESM enforces access controls, the IDS analyzes the audit trails generated by the ESM and other system components (e.g., SMF) to detect patterns indicative of a breach. It often feeds its findings into a broader SIEM solution for enterprise-wide security monitoring and correlation, providing a holistic view of security events across diverse platforms.

Best Practices:

Tailor Rules to z/OS: Configure IDS rules and baselines specifically for the unique characteristics and critical assets of the z/OS environment to minimize false positives and maximize detection accuracy.
Integrate with SIEM: Ensure all z/OS IDS alerts and relevant log data are forwarded to an enterprise-wide SIEM system for centralized monitoring, correlation with other security events, and long-term storage.
Regular Review and Tuning: Periodically review IDS alerts, logs, and detection rules to adapt to evolving threats, optimize performance, and ensure continued effectiveness.
Leverage SMF Data: Maximize the use of SMF records, especially SMF type 80 (RACF events), SMF type 30 (common address space work), and SMF type 42 (dataset activity), as primary data sources for comprehensive security intelligence.
Establish Baselines: Define and maintain a baseline of normal z/OS system and user behavior to effectively identify and flag anomalous activities that could indicate an intrusion.