opn_add_dnsbl_allowlist

THE RISK

Medium Risk

Why opn_add_dnsbl_allowlist needs a policy

The 'add' operation creates or modifies DNS allowlist entries, which is reversible and non-destructive. This qualifies as Write rather than Read (adds data) or Destructive (can be undone). Severity is medium because misconfiguration could weaken security by allowlisting malicious domains, but effects are containable and reversible.

From the tool's definition Tool name 'opn_add_dnsbl_allowlist' uses verb 'add' indicating creation/modification; DNSBL allowlist management modifies DNS blocking behavior by reversibly adding entries to an allowlist.

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

POLICY

How to control opn_add_dnsbl_allowlist

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_add_dnsbl_allowlist:

policy.json

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

opn_add_dnsbl_allowlist 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.

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EXPLORE

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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 opn_add_dnsbl_allowlist

What does the opn_add_dnsbl_allowlist tool do? +

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

How do I enforce a policy on opn_add_dnsbl_allowlist? +

Register the OPNsense MCP Server MCP server in PolicyLayer and add a rule for opn_add_dnsbl_allowlist: 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_add_dnsbl_allowlist? +

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

Can I rate-limit opn_add_dnsbl_allowlist? +

Yes. Add a rate_limit block to the opn_add_dnsbl_allowlist 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_add_dnsbl_allowlist completely? +

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

opn_add_dnsbl_allowlist 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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