vm_stop

THE RISK

High Risk

Why vm_stop needs a policy

This tool triggers an external operation (stopping a VM) whose effects depend on arguments (graceful vs. force shutdown). While not destructive to data, it disrupts service availability and system state. This is Execute rather than Destructive because the VM can be restarted. The 'force-stop' option and potential for service interruption warrant high severity—an agent misusing this could halt critical workloads.

From the tool's definition Tool name 'vm_stop' and description 'Stop a running virtual machine by its ID. Optionally force-stop (power off) instead of graceful shutdown.' indicate execution of control operations on infrastructure.

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

POLICY

How to control vm_stop

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "vm_stop": {
      "limits": [
        {
          "counter": "vm_stop_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

vm_stop stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Truenas — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Truenas tools

Destructive acme_dns_authenticator_delete Delete an ACME DNS authenticator by its ID. Destructive alertservice_delete Delete an alert notification service by its ID. Use alertservice_list to find the ID. Destructive api_key_delete Delete an API key by its numeric ID. Use api_key_list to find the ID. This immediately rev Destructive app_delete Delete/uninstall an app. This is a DESTRUCTIVE operation. The Destructive bootenv_delete Delete a boot environment. This is a DESTRUCTIVE operation — the Destructive certificate_delete Delete a certificate by its ID. This is a DESTRUCTIVE operation — the Destructive cloud_backup_delete Delete a cloud backup task (destructive — requires confirm) Destructive cloudsync_credentials_delete Delete a cloud sync credential

All 279 Truenas tools →

Execute tools on other servers

Android Forensics ADB MCP Server adb_shell_command EMBA-MCP run_emba_scan Frida Game Hacking MCP remove_breakpoint Procmon request_elevation

Go deeper

High-risk tools in Truenas → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about vm_stop

What does the vm_stop tool do? +

Stop a running virtual machine by its ID. Optionally force-stop (power off) instead of graceful shutdown. It is categorised as a Execute tool in the Truenas MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on vm_stop? +

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

What risk level is vm_stop? +

vm_stop is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit vm_stop? +

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

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

vm_stop is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Truenas tool call.

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

CHECK YOUR STACK →