# Don't trust the config: 6 tests that prove your self-hosted AI agent server is locked down > Source: > Published: 2026-10-22 10:03:15+00:00 *Disclosure: I wrote this with AI assistance and checked every command and number against my own test runs.* A personal AI agent on a VPS (OpenClaw, Hermes) tends to get "secured" by reading config files. The config says one thing; the machine does another. Here are six tests I run that check behavior, not settings. Each takes a few minutes. Replace `AGENT_UNIT`, `YOUR_IP` and `USER` with yours. `ufw status` From another machine, not the server itself and not localhost: ``` nmap -Pn -p- -sS YOUR_IP nmap -Pn -sU --top-ports 100 YOUR_IP ``` Expected: only `22/tcp` open. Run it after the agent is started, since the agent's own ports are open by then. If you see the agent gateway port or a dashboard, fix that before anything else. On the server, also check that the agent listens on loopback only: ``` sudo ss -tulnp ``` Everything except sshd should be on loopback: `127.0.0.1` or `::1` for the agent (OpenClaw's gateway is on 18789). Two harmless system entries show up on any Ubuntu: the DNS resolver on `127.0.0.53`/` 127.0.0.54` and the DHCP client on `udp/68`. Open the panel through a tunnel: `ssh -N -L PORT:127.0.0.1:PORT USER@YOUR_IP`. `grep /etc/ssh/sshd_config` misses drop-ins (cloud images often ship one in `sshd_config.d/` that re-enables password login). Ask the daemon: ``` sudo sshd -T | grep -Ei 'passwordauthentication|kbdinteractiveauthentication|permitrootlogin' ``` Expected: `no`, `no`, `no`. Then test it from outside: ``` ssh -o PreferredAuthentications=password -o PubkeyAuthentication=no USER@YOUR_IP ``` You should get `Permission denied` without a password prompt. `systemctl is-active fail2ban` proves a process exists. From a second host, fail a few SSH logins on purpose, then on the server: ``` sudo fail2ban-client status sshd ``` The attacker IP should appear under banned. On my test VMs the ban came after 7 and 127 seconds, depending on timing of retries. Unban yourself afterwards: `sudo fail2ban-client set sshd unbanip IP`. Agents usually run as a user service, so ask the user's systemd, not the system one (the system one will happily print `MainPID=0`): ``` sudo systemctl --user -M USER@ show AGENT_UNIT -p MainPID -p Restart sudo kill -9 ``` The unit should restart on its own (`Restart=always` or `on-failure`), and the agent should answer in Telegram without you touching it. A user service also needs lingering, or it won't survive a reboot: ``` loginctl show-user USER -p Linger ``` I measured 6–7 s for the process and 22–42 s until the first Telegram reply. An alert that was never triggered is a hope. Stop the agent and see whether a message reaches your phone within a couple of minutes. Two traps: the alert must go through your own bot, not the bot of whoever set it up; and no alert can fire if the whole VPS dies, so keep an external uptime ping too. Proof of delivery in a script: the Bot API `sendMessage` response has `"ok": true` and a `message_id`. Neither OpenClaw nor Hermes has a built-in hard spend cap. The cap that holds is on the API key. With OpenRouter: ``` curl -s https://openrouter.ai/api/v1/key -H "Authorization: Bearer $KEY" ``` Look at `limit` (not null) and `limit_reset` (monthly, if you want a monthly ceiling). Don't paste the key into logs or shell history; read it from a root-only file. Take a snapshot of the agent state before each update (OpenClaw: `openclaw backup create --verify`; Hermes: `hermes backup`), pin the version, turn off self-update, and once, on a quiet evening, install a deliberately bad version and make sure you can return. My rollback runs took 1–3.5 minutes including checks. Questions or checks I missed? I'd like to add them. About the author: I set up and harden personal AI agents on VPSes.