svc-dns

A DNS security-testing guide for the system that maps domain names to IP addresses and other records. It covers record discovery, zone transfers, subdomain risks, cache checks, and DNS tunneling detection.

In plain words
What is it for?
Use it to enumerate DNS records and subdomains, test zone transfers, check dangling records that may allow subdomain takeover, and inspect recursion or cached queries.
Why use it?
It helps reveal hidden hosts, accidentally exposed domain data, and DNS settings that could let an attacker redirect or misuse a subdomain.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/s0ld13rr/pentestcode/dns
Any agent
npx skills add s0ld13rr/pentestcode --skill dns
Clone the repo
git clone --depth 1 https://github.com/s0ld13rr/pentestcode

Made for: Claude Code, Codex.

Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 452 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00059 $0.00452
Opus 5 $0.00030 $0.00226
Sonnet 5 $0.00012 $0.00090
Haiku 4.5 $0.00006 $0.00045

Measured yesterday against content hash 4d88c94e3b9a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

svc-dns 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 yesterday.

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.

skills/services/dns/SKILL.md · 61 lines

What it actually says

DNS Attack Reference

Zone Transfer (AXFR)

dig AXFR <domain> @<ns_server>
host -t AXFR <domain> <ns_server>
dnsrecon -d <domain> -a

DNS Enumeration

# Record types
dig <domain> ANY +noall +answer
dig <domain> A +short
dig <domain> AAAA +short
dig <domain> MX +short
dig <domain> NS +short
dig <domain> TXT +short
dig <domain> SOA +short
dig <domain> SRV +short

# Reverse DNS for IP range
dnsrecon -r <cidr>

# Brute force subdomains
dnsrecon -d <domain> -D /usr/share/seclists/Discovery/DNS/subdomains-top1million-5000.txt -t brt
dnsenum <domain>
fierce --domain <domain>

Subdomain Takeover

# Check for dangling CNAME records
dig CNAME <subdomain>
# If CNAME points to unclaimed resource (S3, Heroku, GitHub Pages, Azure) → takeover

# Automated check
subjack -w subdomains.txt -t 20 -o takeover_results.txt
nuclei -t takeovers/ -l subdomains.txt

DNS Cache Poisoning

# Check if recursion is open
dig @<target> example.com +recurse

# Test cache snooping (non-recursive query for cached records)
dig @<target> <popular_domain> +norecurse

DNS Tunneling Detection

# Unusually long subdomains or high query volume to single domain
# Tools: iodine, dnscat2 for establishing DNS tunnels
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. yesterday First seen · 61 lines · 59 tokens per session scan A 4d88c94e3b9a

Subscribe to this mod's changes

svc-dns is a skill published in the GitHub repository s0ld13rr/pentestcode (566 stars, last pushed 11d ago), licensed MIT. It adds 59 tokens to every session and 452 once invoked, about $0.0003 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 2026-08-30.