The Linux Service That Almost Let Attackers Slip In (And How I Found It Just in Time)

Intro:
Even the most hardened Linux systems can fall victim to misconfigured or forgotten services. In one case, a low-priority daemon was the weak link in my server’s armor. Here’s how I discovered it — and what you can learn from it.

1. A Strange Spike in CPU Load

While monitoring server health, I noticed unexplained CPU usage. No cron jobs were running, and user activity was low. Something didn’t add up.

✅ Action Taken:

top

I found an obscure service — rpcbind—consuming resources unexpectedly.

2. Discovering the Culprit with systemd

I traced the service startup:

sudo systemctl status rpcbind
sudo systemctl list-dependencies rpcbind

It had been enabled by a package install I’d done earlier — but I never used it.

3. Checking for Network Exposure

I confirmed the service was listening on a public interface:

sudo ss -tulnp

This exposed my server to potential remote exploits. An open door I didn’t know…