[rsync]

As predicted.

The idea is, in addition to the normal security measures you use with sshd you also hide the service with port knocking.

Nobody anywhere, at any time, has ever suggested using port knocking as the sole means of securing your sshd.

[anon263626]

Port knocking and some even obscurity are valid additional layers of defense-in-depth if combined fundamentals of A3E.

State actors can afford millions to spend on build/buying sploits for [insert technology]. For example, use different standard for OS at edges where possible to reduce attack surface. Preferably scrub network traffic at edges (not just web traffic) and really lock down traffic to remote access boxes.