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Event type

Apache HTTP Error Log

Server errors, warnings, and diagnostic messages

Apache HTTP Server error log entries recording server errors, warnings, configuration issues, client errors, SSL problems, module failures, and script execution errors

PLAIN TEXT 9 fields Medium Generator

error-log http web-server diagnostics troubleshooting
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Overview

What this event covers

Records error conditions, warnings, configuration issues, and diagnostic information from the Apache HTTP Server. Includes server startup/shutdown events, client connection errors, script failures, SSL/TLS issues, module loading problems, and other operational events.

When generated

  • ›Server startup, shutdown, or restart events
  • ›Configuration syntax errors or warnings
  • ›Client request errors (invalid headers, malformed requests)
  • ›Backend script failures (PHP, Python, CGI timeouts or errors)
  • ›SSL/TLS handshake failures or certificate issues
  • ›Module loading failures or dependency errors
  • ›File not found errors (404s for non-logged access requests)
  • ›Resource limit or timeout conditions

Security relevance

High

Compliance

PCI DSS (Requirement 10.2 - System events and errors) HIPAA (Error logging for security events) SOX (Error audit trails) ISO 27001 (A.12.4.1 - Event logging) NIST SP 800-53 (AU-2, AU-3, SI-4 - Audit and monitoring)

Frequency notes

Medium-frequency events during business hours (40 events/hour) with some activity during nights (24 events/hour) due to automated processes and maintenance tasks. Weekends see reduced activity (16 events/hour). Error rates vary significantly based on server health, application stability, and configuration quality.

Resources

Docs and tools

Apache HTTP Server Documentation - Error Log official Apache Error Messages official Apache Log Levels official Troubleshooting Apache Error Logs reference Logwatch System log analyzer and reporter for Apache error logs Fail2Ban Intrusion prevention software that uses Apache error logs to ban malicious IPs Splunk Enterprise log aggregation and analysis platform ELK Stack Elasticsearch, Logstash, and Kibana for log analysis and visualization

Generation

Configuration

Base frequency
20 events/hour
Time patterns
business_hours night_hours weekend
Business hours
2.0x
Night hours
1.2x
Weekend
0.8x

Schema

Field definitions

Field reference for this event type — types, requirements, examples, and allowed values.

timestamp
DateTime Required

Date and time when the error occurred, including microseconds

Source: now() | format_datetime('%a %b %d %H:%M:%S.%f %Y')

Format Day Mon DD HH:MM:SS.microseconds YYYY
Example Fri Dec 20 15:31:09.533710 2025
log_level
String Required

Severity level of the log entry

Source: random_choice(['error', 'warn', 'notice', 'info', 'debug', 'crit', 'alert', 'emerg'])

Format Apache log level
Example error
Values
  • emerg Emergency - System is unusable
  • alert Alert - Action must be taken immediately
  • crit Critical - Critical conditions
  • error Error - Error conditions
  • warn Warning - Warning conditions
  • notice Notice - Normal but significant condition
  • info Informational - Informational messages
  • debug Debug - Debug-level messages
process_id
Integer Required

Process ID of the Apache worker process that logged the event

Source: random_int(1000, 99999)

Format PID
Example 12345
thread_id
Integer Required

Thread ID within the worker process

Source: random_int(100000000, 999999999)

Format Thread ID
Example 139876543210000
client_ip
String Optional

IP address of the client that triggered the error (if applicable)

Source: random_private_ip()

Format IPv4 or IPv6
Example 10.154.52.51
client_port
Integer Optional

Source port of the client connection (if applicable)

Source: random_port(1024, 65535)

Format Port number
Example 54321
error_code
String Optional

Apache error code (AHxxxxx format) identifying the specific error type

Source: Embedded in error message

Format AHxxxxx
Example AH01630
error_message
String Required

Detailed error message describing the issue

Source: random_choice of realistic Apache error messages

Format Free text
Example client denied by server configuration
referer
String Optional

Referring URL that led to the error (if applicable)

Source: Optional: random_choice of referer URLs

Format URL or absent
Example https://apps.example.com/login