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Anthropic-Cybersecurity-Skills/skills/analyzing-tls-certificate-transparency-logs/SKILL.md
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mukul975 27c6414ca5 Add folder anatomy (scripts/agent.py + references/api-reference.md) for 648 cybersecurity skills
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2026-03-10 21:02:12 +01:00

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name, description
name description
analyzing-tls-certificate-transparency-logs 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.

Analyzing TLS Certificate Transparency Logs

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:

  1. Query crt.sh for all certificates matching your domain pattern
  2. Identify certificates with typosquatting variations (Levenshtein distance)
  3. Flag certificates from unexpected CAs
  4. Monitor for wildcard certificates on suspicious subdomains
  5. 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')}")