[toyg]

Just put sshd on a nonstandard port, and 95% of the traffic goes away. Vandals can't be bothered with port-scanning, probably because the risk of getting banned before the scan is even complete is too high.

But I agree that keys are not optional anymore.

[sshine]

I do use non-standard ports and sshd on VPC/VPN interfaces. But for teaching purposes, you are dealt a hand and you have to learn to deal with it.