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threat-modeling.md

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Threat Model Analysis for ossec/ossec-hids

Threat: Agent Compromise and Manipulation (Post-Installation)

  • Threat: Agent Compromise and Manipulation (Post-Installation)

    • Description: After OSSEC agent is installed, an attacker with existing root/administrator access specifically targets the OSSEC agent. The attacker disables the agent, modifies its configuration (ossec.conf, local rules), tampers with monitored files to avoid detection by OSSEC, or uses the agent's communication channel to send false data. This differs from a general host compromise; the attacker's goal is to subvert OSSEC.
    • Impact: Loss of visibility on the compromised host; potential for the attacker to use the compromised agent as a pivot point to attack the OSSEC server; false negatives in security monitoring. OSSEC is rendered ineffective on the compromised host.
    • Affected OSSEC Component: OSSEC Agent (all components: ossec-agentd, ossec-logcollector, ossec-syscheckd, ossec-rootcheck, configuration files).
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Agent Configuration Protection: Restrict file permissions on ossec.conf and local rules files to the absolute minimum. Use a configuration management system to enforce secure configurations and detect unauthorized changes.
      • Agent Integrity Monitoring: Use a separate tool (or a carefully configured, separate OSSEC instance) to monitor the integrity of OSSEC agent binaries and configuration files. This detects tampering.
      • Agent Health Monitoring: Continuously monitor agent connectivity and status from the OSSEC server. Alert on prolonged disconnections or unexpected status changes.
      • Dedicated Agent Network: If feasible, use a dedicated, isolated network for agent-server communication, making it harder for an attacker to reach the agent.

Threat: Agent Spoofing

  • Threat: Agent Spoofing

    • Description: An attacker crafts network packets that mimic legitimate OSSEC agent communications. The attacker sends fabricated log data or control messages to the OSSEC server, without having compromised a legitimate agent.
    • Impact: False positives in security monitoring; potential denial-of-service (DoS) against the OSSEC server; potential for the attacker to trigger specific (misconfigured) active responses on the server.
    • Affected OSSEC Component: OSSEC Server (network communication handling, ossec-remoted), Agent Authentication mechanism.
    • Risk Severity: High
    • Mitigation Strategies:
      • Strong Agent Authentication: Ensure pre-shared keys are strong, unique per agent, and securely managed. Regularly rotate keys. This is the primary defense.
      • Network Segmentation: Isolate the OSSEC server and agent communication on a dedicated network segment, limiting the attacker's ability to reach the server.
      • Firewall Rules: Restrict access to the OSSEC server's listening port (typically UDP 1514) to only authorized agent IP addresses.
      • Rate Limiting: Implement rate limiting on the OSSEC server to prevent an overwhelming influx of messages from a single (potentially spoofed) source.
      • Input Validation: Implement robust input validation on the server to reject malformed or suspicious agent messages, even if they appear to authenticate.

Threat: OSSEC Server Denial of Service (DoS)

  • Threat: OSSEC Server Denial of Service (DoS)

    • Description: An attacker sends a large volume of specifically crafted OSSEC messages (legitimate or illegitimate, but designed to exploit OSSEC's processing) or exploits a vulnerability in the OSSEC server software itself to consume excessive server resources. This is distinct from a generic network DoS.
    • Impact: The OSSEC server becomes unresponsive, preventing it from receiving and processing alerts from legitimate agents. Security monitoring is completely disabled.
    • Affected OSSEC Component: OSSEC Server (all components: ossec-remoted, ossec-analysisd, ossec-monitord, ossec-logcollector, database interaction if used). The specific component exploited depends on the attack.
    • Risk Severity: High
    • Mitigation Strategies:
      • Rate Limiting: Implement strict rate limiting and connection limits on the server, specifically tailored to OSSEC message types.
      • Resource Monitoring: Monitor server resource utilization (CPU, memory, network) and alert on unusual spikes correlated with OSSEC activity.
      • Software Updates: Keep the OSSEC server software meticulously up-to-date to patch any known vulnerabilities in OSSEC components.
      • Load Balancing: Consider using a load balancer in front of multiple OSSEC servers for high availability and resilience against OSSEC-specific attacks.
      • Input Validation: Implement robust input validation and sanitization on all data received by the OSSEC server, even from authenticated agents.

Threat: OSSEC Server Unauthorized Access (Directly Targeting OSSEC)

  • Threat: OSSEC Server Unauthorized Access (Directly Targeting OSSEC)

    • Description: An attacker gains unauthorized access to the OSSEC server, specifically targeting OSSEC components or configurations, rather than general OS access. This might involve exploiting an OSSEC vulnerability, misconfigured OSSEC access controls, or weak OSSEC-related credentials.
    • Impact: Complete compromise of the OSSEC system; access to all collected security logs; ability to modify server configurations, disable monitoring, or create backdoors within OSSEC; data exfiltration of OSSEC logs.
    • Affected OSSEC Component: OSSEC Server (all components), OSSEC configuration files.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strong OSSEC-Specific Authentication: Implement strong authentication and authorization for all access to OSSEC management interfaces (if any) and configuration files.
      • Network Segmentation: Isolate the OSSEC server on a dedicated, highly restricted network segment, limiting access to only authorized systems.
      • Least Privilege (OSSEC Context): Ensure that OSSEC processes run with the minimum necessary privileges. Avoid running OSSEC components as root.
      • Auditing (OSSEC Actions): Enable and monitor audit logs specifically for OSSEC actions (configuration changes, rule modifications, etc.).
      • Regular Security Audits (OSSEC Focus): Conduct regular security audits focused on the OSSEC server and its configuration, not just the underlying OS.

Threat: OSSEC Server Vulnerability Exploitation

  • Threat: OSSEC Server Vulnerability Exploitation

    • Description: An attacker exploits a vulnerability in the OSSEC server software itself (e.g., a buffer overflow in ossec-remoted, a code injection vulnerability in a decoder) to gain control of the server.
    • Impact: Same as "OSSEC Server Unauthorized Access" (Critical). Complete control over the OSSEC server and its data.
    • Affected OSSEC Component: Specific vulnerable component within the OSSEC Server (e.g., ossec-remoted, ossec-analysisd, a specific decoder). The exact component depends on the vulnerability.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Software Updates: Keep the OSSEC server software absolutely up-to-date with the latest security patches. Subscribe to OSSEC security advisories and mailing lists. This is the most critical mitigation.
      • Vulnerability Scanning: Regularly perform vulnerability scans specifically targeting the OSSEC server software.
      • Sandboxing/Containerization: Consider running the OSSEC server (or individual components) in a sandboxed or containerized environment to limit the impact of a successful exploit.
      • Input Validation: Ensure robust input validation and sanitization is performed on all data received by the OSSEC server, even from authenticated agents. This can mitigate some classes of vulnerabilities.

Threat: Rule Evasion (Targeting Specific OSSEC Rules)

  • Threat: Rule Evasion (Targeting Specific OSSEC Rules)

    • Description: An attacker crafts their attacks to specifically avoid triggering known OSSEC rules. This requires knowledge of the deployed OSSEC rule set.
    • Impact: Attacks go undetected by OSSEC, leading to successful compromise, despite OSSEC being deployed.
    • Affected OSSEC Component: OSSEC Server (ossec-analysisd, rules and decoders).
    • Risk Severity: High
    • Mitigation Strategies:
      • Rule Updates: Regularly update OSSEC rules to address new attack techniques and vulnerabilities. Use community-provided rule sets and threat intelligence feeds. Keep up-to-date with the latest attack methods.
      • Rule Testing: Thoroughly test all custom rules (and updated rules) in a non-production environment before deploying them. Use a variety of attack simulations.
      • Anomaly Detection: Implement anomaly-based detection rules in addition to signature-based rules. This helps detect attacks that evade known signatures.
      • Penetration Testing: Perform regular penetration testing, specifically attempting to evade OSSEC detection.
      • Threat Modeling: Continuously update the threat model to identify new potential attack vectors and evasion techniques.

Threat: Misconfigured or Disabled Rules (Impacting OSSEC Functionality)

  • Threat: Misconfigured or Disabled Rules (Impacting OSSEC Functionality)

    • Description: Critical OSSEC rules are accidentally or maliciously disabled, commented out, or misconfigured (e.g., incorrect regular expressions, thresholds set too high), directly impacting OSSEC's ability to detect threats.
    • Impact: Malicious activity goes undetected, leading to successful compromise, because OSSEC is not functioning as intended.
    • Affected OSSEC Component: OSSEC Server (ossec-analysisd, rules and decoders, ossec.conf).
    • Risk Severity: High
    • Mitigation Strategies:
      • Configuration Management: Use a configuration management system (e.g., Ansible, Puppet, Chef) to enforce desired rule settings and prevent unauthorized modifications. This is crucial.
      • Version Control: Use a version control system (e.g., Git) to track changes to rules and configurations, allowing for rollback and auditing.
      • Regular Audits: Regularly audit OSSEC rule configurations specifically to ensure that critical rules are enabled and correctly configured.
      • Change Control: Implement strict change control procedures for all rule modifications, requiring review and approval.
      • Alerting on Configuration Changes: Configure OSSEC to alert on changes to its own configuration files, including rule files.