dns_list_blocked

THE RISK

Low Risk

Why dns_list_blocked needs a policy

This is a Read operation because it retrieves DNS blocking policy information without modifying any state. However, severity is elevated to 'high' rather than 'low' because the blocked domains list reveals the DNS filtering/security policy configuration of the organization.

From the tool's definition 'List blocked DNS zones (domains that are denied)' — retrieves and queries data with no modification. The tool returns information about blocked domains in a hierarchical structure. No side effects or mutations occur.

Documented attack patterns abuse exactly the kind of access dns_list_blocked gives an agent:

POLICY

How to control dns_list_blocked

PolicyLayer is an MCP gateway — it sits between your AI agents and Technitium MCP Secure, and nothing reaches the server without passing your rules. This is the rule we recommend for dns_list_blocked:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "dns_list_blocked": {}
  }
}

dns_list_blocked is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Technitium MCP Secure — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Technitium MCP Secure tools

Destructive dns_delete_cached Delete a specific domain from the DNS cache. Unlike flush, this only removes the specified Destructive dns_delete_record Delete a specific DNS record from a zone. Requires confirm=true to execute. Destructive dns_delete_zone Delete a DNS zone and all its records. Requires confirm=true to execute. Destructive dns_remove_allowed Remove a domain from the allow list. The domain will no longer bypass block lists. Destructive dns_uninstall_app Uninstall a DNS app from the server. Requires confirm=true to execute. Destructive dns_flush_allowed Flush the entire allow list. All allowed domains will be removed. Requires confirm=true to Destructive dns_flush_blocked Flush the entire custom block list. All manually blocked domains will be removed. Requires Execute dns_flush_cache Flush the entire DNS cache. Forces all subsequent queries to be resolved fresh from upstre

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about dns_list_blocked

What does the dns_list_blocked tool do? +

List blocked DNS zones (domains that are denied). Returns a hierarchical tree — call with no domain to see top-level zones, then pass a domain (e.g. It is categorised as a Read tool in the Technitium MCP Secure MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on dns_list_blocked? +

Register the Technitium MCP Secure MCP server in PolicyLayer and add a rule for dns_list_blocked: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Technitium MCP Secure. Nothing to install.

What risk level is dns_list_blocked? +

dns_list_blocked is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit dns_list_blocked? +

Yes. Add a rate_limit block to the dns_list_blocked rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block dns_list_blocked completely? +

Set action: deny in the PolicyLayer policy for dns_list_blocked. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides dns_list_blocked? +

dns_list_blocked is provided by the Technitium MCP Secure MCP server (rosschurchill/technitium-mcp-secure). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Technitium MCP Secure tool call.

Start from Technitium MCP Secure, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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