Configuration is based on:
https://coreos.com/os/docs/latest/customizing-sshd.html

The specific SSHD config is:

    # Use most defaults for sshd configuration.
    UsePrivilegeSeparation sandbox
    Subsystem sftp internal-sftp
    ClientAliveInterval 180
    UseDNS no
    UsePAM yes
    PrintLastLog no # handled by PAM
    PrintMotd no # handled by PAM
    AuthenticationMethods publickey

This will prevent security scanners from triggering.