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.
Is public key authentication not good enough? Tailscale is cool but can be tedious if you also use other VPNs
Yeah that's what I have too. One of my servers is exposed with key auth and I just tunnel to other servers from there. A few MB egress is nothing compared with the amount of spam my webserver needs to deal with