mukul975/analyzing-tls-certificate-transparency-logs
skills/analyzing-tls-certificate-transparency-logs/SKILL.md
Queries Certificate Transparency logs via crt.sh and pycrtsh to detect phishing domains, unauthorized certificate issuance, and shadow IT. Monitors newly issued certificates for typosquatting and brand impersonation using Levenshtein distance. Use for proactive phishing domain detection and certificate monitoring.
$ install --global
skillsauthnpx skillsauth add mukul975/anthropic-cybersecurity-skills analyzing-tls-certificate-transparency-logsInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
Security Scan Results
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Scanners in report
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TrivyContainer and dependency vulnerability scanner
95%
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SemgrepStatic code analysis for vulnerabilities
95%
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mcp-scan (Snyk)Model Context Protocol security validation
95%
Skipped
Snyk (dep)Open source security scanning
50%
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Socket.devSupply chain security analysis
50%
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VirusTotalMulti-engine malware detection
50%
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CrowdStrikeAdvanced threat intelligence
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OSV-ScannerOpen Source Vulnerability database check
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OWASP Dep-Check
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Last scanned: Jun 21, 2026, 3:53 AM121.5s3 files scanned
SKILL.md
- name:
- Phishing
- description:
- Queries Certificate Transparency logs via crt.sh and pycrtsh to detect
- domain:
- cybersecurity
- subdomain:
- security-operations
- version:
- 1.1
- author:
- mahipal
- license:
- Apache-2.0
- - id:
- T1660
- tactic:
- initial-access
- source:
- attack
Analyzing TLS Certificate Transparency Logs
When to Use
- When investigating security incidents that require analyzing tls certificate transparency logs
- 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
Query crt.sh Certificate Transparency database to find certificates issued for domains similar to your organization's brand, detecting phishing infrastructure.
from pycrtsh import Crtsh
c = Crtsh()
# Search for certificates matching a domain
certs = c.search("example.com")
for cert in certs:
print(cert["id"], cert["name_value"])
# Get full certificate details
details = c.get(certs[0]["id"], type="id")
Key analysis steps:
- Query crt.sh for all certificates matching your domain pattern
- Identify certificates with typosquatting variations (Levenshtein distance)
- Flag certificates from unexpected CAs
- Monitor for wildcard certificates on suspicious subdomains
- Cross-reference with known phishing infrastructure
Examples
from pycrtsh import Crtsh
c = Crtsh()
certs = c.search("%.example.com")
for cert in certs:
print(f"Issuer: {cert.get('issuer_name')}, Domain: {cert.get('name_value')}")
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