Detecting SSH Access Proxies with Nmap

A port is open. You see it. You know what it means. SSH is live, and the path runs straight through an access proxy.

Nmap makes this visible in seconds. A single scan can reveal SSH endpoints hiding behind a proxy layer. With proper command flags, you can map the proxy, confirm its banners, and detect fingerprint mismatches. Experienced operators use nmap -p 22 --script ssh-hostkey,ssh2 to collect keys, validate them, and check if the target is fronted by a proxy service. Adding --script ssh-auth-methods exposes authentication options before you connect.

An SSH Access Proxy changes the rules. It can mask the real host, control traffic flows, and enforce policy. Nmap’s scripting engine detects these layers and shows you exactly how the connection behaves. Look for indications in the scan output: uniform host keys across multiple IPs, non-standard version strings, or latency patterns that match proxy routing. Coupled with version detection (-sV), this gives you hard data to decide your next step.

The workflow is simple but precise:

1. Identify the endpoint with Nmap.
2. Capture host keys and authentication methods.
3. Compare results across known hosts to confirm proxy presence.
4. Record any anomalies in version, headers, or latency profiles.

These scans are fast, but dangerous to run without clear rules of engagement. Always check legal boundaries before probing live systems. Every open SSH port is potential entry, but every proxy layer is potential control.

If you need to set up, test, or demo an Nmap SSH Access Proxy workflow, hoop.dev can get it running in minutes. See it live, run your own scans, and take control of your SSH visibility.