apply_nat_rule · AF_ MCP: Risk & Policy

WHAT IT DOES

What apply_nat_rule does on AF_MCP

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

WHY IT NEEDS A POLICY

Why apply_nat_rule needs a policy

This tool modifies network routing/translation rules (NAT configuration) on security devices. While changes are theoretically reversible (can be undone by removing/updating the rule), the blast radius is high because incorrect NAT rules can disrupt network traffic, redirect traffic to attackers, or bypass security policies.

From the tool's definition Tool description: '提交 NAT 规则变更' (submit NAT rule changes). Performs network address translation rule modifications that are reversible. Requires prior preview_nat_rule call and confirmed=True flag, indicating a write operation with confirmation mechanism.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_nat_rule Rate-limited

apply_nat_rule 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": {
    "apply_nat_rule": {
      "limits": [
        {
          "counter": "apply_nat_rule_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 AF_MCP, so you can run agents against it safely.

FAQ

Questions about apply_nat_rule

What does the apply_nat_rule tool do? +

提交 NAT 规则变更。需先调用 preview_nat_rule，确认后以 confirmed=True 调用。. It is categorised as a Write tool in the AF_MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on apply_nat_rule? +

Register the AF_ MCP server in PolicyLayer and add a rule for apply_nat_rule: 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 AF_MCP. Nothing to install.

What risk level is apply_nat_rule? +

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

Can I rate-limit apply_nat_rule? +

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

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

apply_nat_rule is provided by the AF_ MCP server (xiaqijun/af_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.