AI agents call find_external_tier_zero_users to retrieve information from BloodHound MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries BloodHound's Active Directory attack path database to identify a specific subset of high-risk users (tier zero with external access). It retrieves sensitive information about AD security posture but does not execute commands, modify data, or cause irreversible changes.
From the tool's definition Tool name 'find_external_tier_zero_users' performs a query/lookup operation to identify users in tier zero (highest privilege) with external access.
Documented attack patterns abuse exactly the kind of access find_external_tier_zero_users gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and BloodHound MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for find_external_tier_zero_users:
{
"version": "1",
"default": "deny",
"tools": {
"find_external_tier_zero_users": {}
}
}find_external_tier_zero_users is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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find_external_tier_zero_users. It is categorised as a Read tool in the BloodHound MCP MCP Server, which means it retrieves data without modifying state.
Register the BloodHound MCP server in PolicyLayer and add a rule for find_external_tier_zero_users: 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 BloodHound MCP. Nothing to install.
find_external_tier_zero_users is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the find_external_tier_zero_users 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 find_external_tier_zero_users. 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.
find_external_tier_zero_users is provided by the BloodHound MCP server (mordavid/bloodhound-mcp-ai). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from BloodHound MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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75 BloodHound MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.