In the past two weeks I set up a new VPS, and I run a small experiment. I share the results for those who are curious.
Consider that this is a backup server only, meaning that there is no outgoing traffic unless a backup is actually to be recovered, or as we will see, because of sshd.
I initially left the standard “port 22 open to the world” for 4-5 days, I then moved sshd to a different port (still open to the whole world), and finally I closed everything and turned on tailscale. You find a visualization of the resulting egress traffic in the image. Different colors are different areas of the world. Ignore the orange spikes which were my own ssh connections to set up stuff.
Main points:
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there were about 10 Mb of egress per day due just to sshd answering to scanners. Not to mention the cluttering of access logs.
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moving to a non standard port is reasonably sufficient to avoid traffic and log cluttering even without IP restrictions
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Tailscale causes a bit of traffic, negligible of course, but continuous.
The reason a VPN is better to expose than SSH, is the feedback.
If someone tries connecting to your SSH with the wrong key or password, they get a nice and clear permission denied. They now know that you have SSH, and which version. Which might allow them to find a vulnerability.
If someone connects to your wireguard with the wrong key, they get zero response. Exactly as if the port had not been open in the first place. They have no additional information, and they don’t even know that the port was even open.
Try running your public IP through shodan.io, and see what ports and services are discovered.