Imported from mukul975/anthropic-cybersecurity-skills (skills/analyzing-web-server-logs-for-intrusion/SKILL.md) via skills.sh. Install upstream with npx skills add mukul975/anthropic-cybersecurity-skills --skill analyzing-web-server-logs-for-intrusion. Copyright stays with the author (Apache-2.0).

Analyzing Web Server Logs for Intrusion

When to Use

• When investigating security incidents that require analyzing web server logs for intrusion
• When building detection rules or threat hunting queries for this domain
• When SOC analysts need structured procedures for this analysis type
• When validating security monitoring coverage for related attack techniques

Prerequisites

• Familiarity with security operations concepts and tools
• Access to a test or lab environment for safe execution
• Python 3.8+ with required dependencies installed
• Appropriate authorization for any testing activities

Instructions

1. Install dependencies: pip install geoip2 user-agents
2. Collect web server access logs in Combined Log Format (Apache) or Nginx default format.
3. Parse each log entry extracting: IP, timestamp, method, URI, status code, response size, user-agent, referer.
4. Apply detection rules:
   • SQL injection: UNION SELECT, OR 1=1, ' OR ', hex encoding patterns
   • LFI/Path traversal: ../, /etc/passwd, /proc/self, php://filter
   • XSS: <script>, javascript:, onerror=, onload=
   • Scanner signatures: nikto, sqlmap, dirbuster, gobuster, wfuzz user-agents
   • Brute force: >50 POST requests to login endpoints from same IP in 5 minutes
5. Enrich with GeoIP data and generate a prioritized findings report.

python scripts/agent.py --log-file /var/log/nginx/access.log --geoip-db GeoLite2-City.mmdb --output web_intrusion_report.json

Examples

Detect SQLi in URI

192.168.1.100 - - [15/Jan/2024:10:30:45 +0000] "GET /products?id=1' UNION SELECT username,password FROM users-- HTTP/1.1" 200 4532

Scanner User-Agent Detection

Nikto/2.1.6, sqlmap/1.7, DirBuster-1.0-RC1, gobuster/3.1.0