Plc-SetSystemTime

THE RISK

Medium Risk

Why Plc-SetSystemTime needs a policy

This tool writes/modifies the system time on an industrial PLC controller. While potentially reversible (time can be set again), changing PLC system time can disrupt time-critical industrial control logic, scheduled operations, alarm timestamps, and synchronization with other systems.

From the tool's definition 'set the system time of the CPU (PLC local time)' — modifies the PLC's system clock

Documented attack patterns abuse exactly the kind of access Plc-SetSystemTime gives an agent:

POLICY

How to control Plc-SetSystemTime

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "Plc-SetSystemTime": {
      "limits": [
        {
          "counter": "plc-setsystemtime_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

Plc-SetSystemTime 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.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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Write tools on other servers

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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 Plc-SetSystemTime

What does the Plc-SetSystemTime tool do? +

Use this API method to set the system time of the CPU (PLC local time). To call the Plc.SetSystemTime method, you need the. It is categorised as a Write tool in the ThinkPLC-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 Plc-SetSystemTime? +

Register the ThinkPLC- MCP server in PolicyLayer and add a rule for Plc-SetSystemTime: 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 ThinkPLC-MCP. Nothing to install.

What risk level is Plc-SetSystemTime? +

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

Can I rate-limit Plc-SetSystemTime? +

Yes. Add a rate_limit block to the Plc-SetSystemTime 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 Plc-SetSystemTime completely? +

Set action: deny in the PolicyLayer policy for Plc-SetSystemTime. 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 Plc-SetSystemTime? +

Plc-SetSystemTime is provided by the ThinkPLC- MCP server (mrwan84/thinkplc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every ThinkPLC-MCP tool call.

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

CHECK YOUR STACK →