I run a backup script to backup my VPS’s every night using rsync. On one of my VPS’s I was seeing the error “ssh: connect to host … port 22: Connection refused” at seeming random points.
It took me a while to track down the fact that lylix.com (the provider of my VPS) block multiple inbound and outbound ssh connections to a server made over a short period of time.
Whilst this is probably useful for some people, and will offer their VPS some protection from brute force login attempts, it broke my script! 🙂