opn_list_dns_forwards

THE RISK

Low Risk

Why opn_list_dns_forwards needs a policy

This tool retrieves and displays DNS forwarding zone configurations from OPNsense's Unbound DNS service. It is purely informational, performs no state changes, executes no commands, and has no destructive potential. The blast radius of misuse is minimal — an attacker gains only read access to DNS forwarding configuration, which is already visible to authenticated users on the system.

From the tool's definition Tool name contains 'list' and description states 'List Unbound DNS forward zones' — a query operation that retrieves configuration data without modification or side effects.

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

POLICY

How to control opn_list_dns_forwards

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

policy.json

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

opn_list_dns_forwards 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 OPNsense MCP Server — 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

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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 opn_list_dns_forwards

What does the opn_list_dns_forwards tool do? +

List Unbound DNS forward zones (domain-specific DNS servers). It is categorised as a Read tool in the OPNsense MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on opn_list_dns_forwards? +

Register the OPNsense MCP Server MCP server in PolicyLayer and add a rule for opn_list_dns_forwards: 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 OPNsense MCP Server. Nothing to install.

What risk level is opn_list_dns_forwards? +

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

Can I rate-limit opn_list_dns_forwards? +

Yes. Add a rate_limit block to the opn_list_dns_forwards 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 opn_list_dns_forwards completely? +

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

opn_list_dns_forwards is provided by the OPNsense MCP Server MCP server (lucamarien/opnsense-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every OPNsense MCP Server tool call.

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

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