Information
The /etc/hosts.allow file specifies which IP addresses are permitted to connect to the host. It is intended to be used in conjunction with the /etc/hosts.deny file. The /etc/hosts.allow file supports access control by IP and helps ensure that only authorized systems can connect to the server.
Solution
Create /etc/hosts.allow- # echo 'ALL- <net>/<mask>, <net>/<mask>, ...' >/etc/hosts.allow where each <net>/<mask> combination (for example, '192.168.1.0/255.255.255.0') represents one network block in use by your organization that requires access to this system.