Allow only certain hosts to ssh into your Linux box

sample /etc/hosts.allow file:

# 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: 192.168.100. ALLOW
sshd: 192.168.10. ALLOW
sshd: ALL: DENY