UNIX for Dummies Questions & Answers

Hi there,

For /etc/hosts.deny was it used to deny access from the internet?

I am not sure what you mean: "/etc/hosts.deny" is part of the TCP wrapper software, which exists for many operating systems. It allows (together with "/etc/hosts.allow") to control and restrict access from certain hosts, not necessarily deny it. For instance one could allow for a certain host to access the local host via ftp but deny access via telnet.

Note that only protocols with an initial handshake can be controlled (which is true for TCP but not for UDP for instance).

I hope this helps.

bakunin

Hello Alvinoo,

Just want to add a little more here. 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. ITS recommends that to start with, you 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 virginia.edu network domain, but no others.

Following is an example for same.
/etc/hosts.allow

Code:

 #
 # hosts.allow   This file describes the names of 
 #               the hosts that 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: .virginia.edu

Code:

 #
 # hosts.deny    This file describes the names of
 #               the hosts that 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

Configuration shown in the above /etc/hosts.allow file, to permit connections to any services protected by the tcpd or sshd from only systems within the virginia.edu domain. Also for more information on same, you can go through the following link too.
hosts.deny(5) - Linux man page

Hope this helps.

Thanks,
R. Singh