AI agents invoke scan_url to trigger actions in YaraFlux MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Scanning a URL involves fetching remote content (an external network operation) and running YARA analysis against it. This triggers external operations whose effects depend on arguments (which URL is provided), placing it in the Execute category. Severity is high because an AI agent could be directed to scan arbitrary URLs, potentially causing unwanted network requests to sensitive or malicious endpoints.
From the tool's definition Tool name 'scan_url' on a server described as performing 'YARA rule-based threat analysis on files and URLs' — implies fetching and scanning external URLs.
Documented attack patterns abuse exactly the kind of access scan_url gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and YaraFlux MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for scan_url:
{
"version": "1",
"default": "deny",
"tools": {
"scan_url": {
"limits": [
{
"counter": "scan_url_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}scan_url 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.
Free to start. No card required.
scan_url. It is categorised as a Execute tool in the YaraFlux MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the YaraFlux MCP Server MCP server in PolicyLayer and add a rule for scan_url: 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 YaraFlux MCP Server. Nothing to install.
scan_url is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the scan_url 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 scan_url. 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.
scan_url is provided by the YaraFlux MCP Server MCP server (threatflux/yaraflux). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from YaraFlux MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
20 YaraFlux MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.