pfsense_update_system_dns · Pfsense MCP: Risk & Policy

WHAT IT DOES

What pfsense_update_system_dns does on Pfsense

AI agents use pfsense_update_system_dns to create or update resources in Pfsense — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Pfsense environment.

WHY IT NEEDS A POLICY

Why pfsense_update_system_dns needs a policy

The tool name suggests it modifies the system DNS configuration on a pfSense firewall. Changing DNS settings can redirect all DNS resolution for the network, enabling traffic interception or denial of service. Severity is high due to blast radius on network security. Confidence is moderate because the description is empty, so we rely solely on the tool name.

From the tool's definition Tool name: pfsense_update_system_dns — 'update' implies modification; 'system_dns' implies DNS resolver/forwarder configuration on the firewall

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

pfsense_update_system_dns Rate-limited

pfsense_update_system_dns 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Pfsense, so you can run agents against it safely.

FAQ

Questions about pfsense_update_system_dns

What does the pfsense_update_system_dns tool do? +

pfsense_update_system_dns. It is categorised as a Write tool in the Pfsense MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on pfsense_update_system_dns? +

Register the Pfsense MCP server in PolicyLayer and add a rule for pfsense_update_system_dns: 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 Pfsense. Nothing to install.

What risk level is pfsense_update_system_dns? +

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

Can I rate-limit pfsense_update_system_dns? +

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

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

pfsense_update_system_dns is provided by the Pfsense MCP server (abl030/pfsense-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.