dns_block_domain

THE RISK

Medium Risk

Why dns_block_domain needs a policy

This tool modifies DNS server behavior by adding a domain to a blocklist, causing all queries for that domain to be denied. It's a Write operation (creates/modifies a blocking rule) rather than Destructive since it can presumably be reversed (unblocked). However, severity is high because misuse could block legitimate domains, causing widespread service disruption for users relying on that DNS server.

From the tool's definition Block a domain name. Queries to this domain will be denied by the DNS server.

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

POLICY

How to control dns_block_domain

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_block_domain:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "dns_block_domain": {
      "limits": [
        {
          "counter": "dns_block_domain_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

dns_block_domain stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. 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.

LIMIT THIS TOOL →

Free to start. No card required.

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

All 39 Technitium MCP Secure tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about dns_block_domain

What does the dns_block_domain tool do? +

Block a domain name. Queries to this domain will be denied by the DNS server. It is categorised as a Write tool in the Technitium MCP Secure MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on dns_block_domain? +

Register the Technitium MCP Secure MCP server in PolicyLayer and add a rule for dns_block_domain: 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_block_domain? +

dns_block_domain is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit dns_block_domain? +

Yes. Add a rate_limit block to the dns_block_domain 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_block_domain completely? +

Set action: deny in the PolicyLayer policy for dns_block_domain. 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_block_domain? +

dns_block_domain 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.

CHECK YOUR STACK →