AI agents use create_firewall_preset to create or update resources in OPNSense MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your OPNSense MCP Server environment.
Creating firewall rules is a reversible write operation that modifies the firewall's security posture by adding new access control policies. While not irreversible (rules can be deleted), misconfiguration could block legitimate traffic or accidentally permit unauthorized access, justifying 'high' severity.
From the tool's definition Tool name 'create_firewall_preset' and description 'Create a firewall rule from a preset' indicate creation of firewall rules, which are network access control policies.
Documented attack patterns abuse exactly the kind of access create_firewall_preset gives an agent:
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 create_firewall_preset:
{
"version": "1",
"default": "deny",
"tools": {
"create_firewall_preset": {
"limits": [
{
"counter": "create_firewall_preset_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_firewall_preset 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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Create a firewall rule from a preset. 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.
Register the OPNSense MCP Server MCP server in PolicyLayer and add a rule for create_firewall_preset: 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.
create_firewall_preset is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the create_firewall_preset 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.
Set action: deny in the PolicyLayer policy for create_firewall_preset. 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.
create_firewall_preset is provided by the OPNSense MCP Server MCP server (vespo92/opnsensemcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 196 OPNSense MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
196 OPNSense MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.