The file /etc/hosts.deny on Unix/Linux can block login attempts based on counties. The below is a simple host.deny file to block all countries but your own ( in my case Australia), sure this is not the whole answer to securing a system but it sure cuts down the number of hack attempts.

sudo vi /etc/hosts.allow

#
# hosts.deny This file describes the names of the hosts which are
# *not* allowed to use the local INET services, as decided
# by the '/usr/sbin/tcpd' server.
#
# We will block *all*