iptables 방화벽을 비활성화 한 경우 유용한 방화벽 설정
신뢰할 수 있는 IP만 접속할 수 있는 화이트리스트를 구성할 때 유용함


#
# hosts.allow	This file describes the names of the hosts which are
#		allowed to use the local INET services, as decided
#		by the '/usr/sbin/tcpd' server.
#
sshd: 150.183.
sshd: 172.16.
sshd: 210.117.
sshd: 210.125.
sshd: 220.66.
sshd: 220.92.


#
# 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.
#

sshd: ALL


# CentOS
sudo service sshd restart
# Ubuntu
sudo service ssh restart