hosts.allow and hosts.deny
To restrict access to your Unix or Linux machine, you must modify the
/etc/hosts.allow and /etc/host.deny files. These files are used by the
tcpd (tcp wrapper) and sshd programs to decide whether or not to accept
a connection coming in from another IP address. Restrict access to only
those network addresses you are certain should be allowed access. The
following two example files allow connections from any address in the
cracker.com network domain, but no others.
/etc/hosts.allow
Using the configuration shown in the following /etc/hosts.allow file, to
permit connections to any services protected by the tcpd or sshd from
only systems within the virginia.edu domain:
#
# 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.
#
# Only allow connections within the virginia.edu domain.
ALL: .cracker.com
/etc/hosts.deny
Suggested: /etc/hosts.deny file content. With this configuration, access
to your machine from all hosts is denied, except for those specified in
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.
#
# deny all by default, only allowing hosts or domains listed in
hosts.allow.
ALL: ALL
Reference: http://its.virginia.edu/unixsys/sec/hosts.html
