Linux Security

Disable Portmap Service

You should disable the portmap service. You can check if it is available:

$ rpcinfo -T udp -p <ip>
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper

Or check with systemctl list-units --type=service.

Uninstall with: apt-get remove rpcbind --auto-remove

Disable IPv6

sshd security

# own settings
PasswordAuthentication no
PermitEmptyPasswords no