ShieldDNS MCP server

Let AI agents check a link before opening it.

shielddns-mcp is a small, open-source Model Context Protocol server that gives AI assistants and agents (Claude, Cursor, any MCP client) safe DNS tools backed by ShieldDNS, a free European public resolver with malware / phishing / tracking protection, DNSSEC validation and a zero-log policy.

Italiano più sotto.

Tools

The server also gives the agent short instructions: check unfamiliar domains before visiting them and follow the advice field.

What the risk score looks at (v0.1)

• ShieldDNS blocklist: about 955,000 domains from 8 threat-intelligence, ads and tracking sources. ShieldDNS marks blocked answers with Extended DNS Error 15 "Blocked"; on nodes without EDE the server recognises the block from the answer itself (NXDOMAIN without SOA).

• DNSSEC: validated, unsigned, or invalid signature (possible tampering, EDE 6-12).

• Name-only signals, computed locally:

  • look-alikes of frequently impersonated brands (paypa1.com, arnazon.com, paypal-secure-login.com, paypal.com.verify-account.net);

  • mixed scripts and IDN tricks (аpple.com with a Cyrillic "а");

  • random-looking names typical of malware domain generation algorithms (DGA);

  • very long or heavily hyphenated names.

• does_not_exist is reported separately: for an agent it often means a mistyped or hallucinated link.

Example:

{
  "domain": "paypal-secure-login.com",
  "verdict": "resolves",
  "risk_score": 40,
  "risk_level": "medium",
  "advice": "caution",
  "reasons": [
    {"code": "brand_with_lure_words", "weight": 40,
     "detail": "the name evokes the brand \"paypal\" but is not one of its official domains (paypal.com, paypal.me)"}
  ],
  "dnssec": "not validated (unsigned or unavailable)"
}

Related MCP server: CyberMCP

Privacy

• The server runs on your machine. It sends only DNS queries, only to ShieldDNS, over HTTPS (secure2.shielddns.eu, fallback secure.shielddns.eu). service_status additionally downloads the public status files from shielddns.eu.

• ShieldDNS does not log queries or client IP addresses.

• No telemetry, no accounts, no API keys.

Install

Requires uv (brew install uv on macOS, or curl -LsSf https://astral.sh/uv/install.sh | sh).

From GitHub:

uvx --from git+https://github.com/shielddns/shielddns-mcp shielddns-mcp

From a local copy:

uvx --from /path/to/shielddns-mcp shielddns-mcp

The server speaks MCP over stdio: run it from an MCP client, not by hand.

Claude Desktop

~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

{
  "mcpServers": {
    "shielddns": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/shielddns/shielddns-mcp", "shielddns-mcp"]
    }
  }
}

Claude Code

claude mcp add shielddns -- uvx --from git+https://github.com/shielddns/shielddns-mcp shielddns-mcp

Cursor and other clients

Use the same command / args as above in the client's MCP configuration.

Test without an MCP client

cd shielddns-mcp
uv run --with . python examples/smoke_test.py
uv run --with . python examples/smoke_test.py some-domain.example --json

Or with the MCP Inspector: npx @modelcontextprotocol/inspector uvx --from . shielddns-mcp

Configuration (optional)

Limits

• The score is a decision aid, not a guarantee. A clean result does not mean a site is trustworthy; a caution result can be a false positive (e.g. a legitimate site that mentions a brand).

• The brand list is small and curated (signals.py); contributions welcome.

• Coming next: a server-side ShieldDNS risk API (domain age, threat source categories, more brands), used automatically by this server when available.

Development

uv run --with '.[test]' pytest

License: MIT.

Italiano

ShieldDNS MCP server permette agli assistenti e agli agenti AI di controllare un link prima di aprirlo, usando ShieldDNS, il resolver pubblico europeo gratuito con protezione da malware, phishing e tracciamento, validazione DNSSEC e politica zero-log.

• check_domain: dice se un dominio o un URL è sicuro, con un verdetto, un punteggio di rischio da 0 a 100 con le motivazioni e un consiglio: ok_to_open, caution o do_not_open.

• resolve: risolve un nome tramite ShieldDNS (DNS-over-HTTPS, DNSSEC, blocco delle minacce).

• service_status: stato pubblico dei due nodi.

Il punteggio considera: la blocklist di ShieldDNS (circa 955.000 domini, segnalati con l'errore DNS esteso 15 "Blocked"), la validità della firma DNSSEC, le imitazioni di marchi noti, i nomi con alfabeti mescolati e i nomi generati a caso dal malware. "Il dominio non esiste" viene segnalato a parte: per un agente spesso significa un link sbagliato o inventato.

Privacy: il server gira sul tuo computer e invia solo query DNS a ShieldDNS, via HTTPS. ShieldDNS non registra le query né gli indirizzi IP. Nessuna telemetria, nessun account, nessuna chiave.

Installazione: vedi sopra (Claude Desktop, Claude Code, Cursor). Serve uv.