auditing-tls-certificate-transparency-logs

auditing-tls-certificate-transparency-logs is a skill for Claude Code from 26zl/cybersec-toolkit. It costs 104 tokens per session (3,373 once invoked), scanned A, original, MIT.

A security monitoring guide for Certificate Transparency logs, public records of TLS certificates issued for websites. It helps track certificates for domains you own and spot unexpected or suspicious issuances.

In plain words
What is it for?
Monitoring certificate activity for owned domains, discovering subdomains, checking Certificate Authority compliance, and sending alerts about new certificates.
Why use it?
It can reveal rogue certificates, phishing domains, and previously unknown subdomains before they become larger security problems.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Part of the cybersec-toolkit plugin — 197 skills, 2 hooks, 1 MCP server shipped together

Good fit Monitoring certificate activity for owned domains, discovering subdomains, checking Certificate Authority compliance, and sending alerts about new certificates.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add 26zl/cybersec-toolkit --skill auditing-tls-certificate-transparency-logs
Clone the repo
git clone --depth 1 https://github.com/26zl/cybersec-toolkit

Made for: Claude Code.

Or install cybersec-toolkit, the plugin that ships this one along with the rest of its 197 skills, 2 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for auditing-tls-certificate-transparency-logs

README.md
[![agentmods](https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs/github.svg)](https://agentmods.dev/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs)
Your own site
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for auditing-tls-certificate-transparency-logs

Your own site · 80×15
<a href="https://agentmods.dev/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs"><img src="https://agentmods.dev/badge/skills/26zl/cybersec-toolkit/auditing-tls-certificate-transparency-logs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 104 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,373 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00104 $0.03373
Opus 5 $0.00052 $0.01687
Sonnet 5 $0.00021 $0.00675
Haiku 4.5 $0.00010 $0.00337

Measured 8d ago against content hash 9885e9fb0f54, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

auditing-tls-certificate-transparency-logs scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/agent.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

.claude/skills/auditing-tls-certificate-transparency-logs/SKILL.md · 204 lines

How it starts

The opening of the file, as written. The whole thing — 204 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Auditing TLS Certificate Transparency Logs

When to Use

  • Monitoring owned domains for unauthorized or unexpected certificate issuance by unknown Certificate Authorities
  • Discovering subdomains and hidden services through certificates logged in public CT logs
  • Detecting phishing infrastructure that uses look-alike domain certificates (typosquatting, homograph attacks)
  • Auditing Certificate Authority compliance by verifying all issued certificates appear in CT logs as required by browser policies
  • Building continuous certificate monitoring into a security operations pipeline with alerting for new issuances

Do not use for attacking or disrupting Certificate Authorities, for scraping CT logs in violation of rate limits or terms of service, or as the sole method of subdomain enumeration without corroborating results through DNS verification.

Prerequisites

  • Python 3.10+ with requests, cryptography, and pyOpenSSL libraries installed
  • Network access to crt.sh (HTTPS) and public CT log servers
  • A list of domains to monitor (owned domains, brand variations, typosquat candidates)
  • SMTP credentials or webhook URL for alerting on new certificate discoveries
  • Basic understanding of X.509 certificate structure and TLS certificate chain validation

Workflow

Step 1: Domain Inventory and Baseline

Build the initial certificate inventory for monitored domains:

  • Define monitoring scope: List all owned root domains, registered brand names, and known subsidiaries. Include wildcard patterns (%.example.com) for comprehensive subdomain coverage.
  • Query crt.sh for historical certificates: Use the crt.sh JSON API to retrieve all known certificates for each domain. The API endpoint https://crt.sh/?q=%.example.com&output=json returns certificates matching the wildcard pattern with fields including issuer_ca_id, issuer_name, common_name, name_value, not_before, not_after, and serial_number.
  • Build baseline database: Store the initial certificate set in a local SQLite database with columns for certificate ID, domain, issuer, validity dates, SANs (Subject Alternative Names), and first-seen timestamp. This baseline prevents alerting on already-known certificates.
  • Identify authorized CAs: From the baseline, extract the set of Certificate Authorities that have legitimately issued certificates for your domains. Any future issuance from a CA not in this set triggers a high-priority alert.
  • Map subdomains: Extract all unique subdomains from the name_value field across all certificates to build an initial subdomain inventory.

Read the full file on GitHub · 204 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 204 lines · 104 tokens per session scan A 9885e9fb0f54

Subscribe to this mod's changes

auditing-tls-certificate-transparency-logs is a skill published in the GitHub repository 26zl/cybersec-toolkit (54 stars, last pushed yesterday), licensed MIT. It adds 104 tokens to every session and 3,373 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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