Has MSFT done anything with XP Lately?

Question

My children's computers run XP as an application on their LINUX boxes.  Recently, my daughter notices that her host file exclusion list is being ignored, i.e. she is getting to sites that she does not want to see on her machine.:

She coded her *&#92;etc&#92;hosts  file is as follows:

# Copyright (c) 1998 Microsoft Corp.
# This is a sample HOSTS file used by Microsoft TCP/IP stack for Windows98
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
# For example:
#
# 102.54.94.97 rhino.acme.com     # source server
#  38.25.63.10 x.acme.com      # x client host
  127.0.0.1    localhost
  127.0.0.1    www.asstr.org      # Stupid site
  127.0.0.1    www.bing.com     # stop MSTF spying.  
  127.0.0.1        bing.com        # stop MSTF spying.

Yet She still gets Bing.com and other blocked files.  

This was working several months ago.  

What has changed in XP

ʄaçade · Accepted Answer

First of all, that file is "/etc/hosts".

Second, it is NOT the "host file exclusion list".  It is the local host file, part of the resolver.  Its purpose is to identify which IP address is associated with those DNS domain names.  The file is not needed at all if DNS is in use.  But it does serve as a fall-back  address resolver for times when DNS is non-responsive.

The localhost address, 127.0.0.1, is the address that refers to the current machine.  That is, is the the computer's address for talking to itself.  That is why tying certain external domain addresses back to the localhost is such a handy blocking tool.  You are fooling the network layer into talking to itself rather than to Bing.com or some other bad place.

Here is the "catch".  That trick only works if the local host file (/etc/hosts) is being read FIRST.  Only id the file is consulted BEFORE DNS is queried.  If DNS is asked for an address (given the name) and it answers, then the local /etc/hosts file is going to be ignored.

Look at the /etc/nsswitch.conf file (NS Switch -- Name Service Switch) and make sure that "files" appears BEFORE "dns" does.

grep  hosts:  /etc/nsswitch.conf

hosts: files mdns4_minimal [NOTFOUND=return] dns
_____^^^^^
The "files" keyword appears first.  DNS appears later further   to the right.

Finally, if a Microsoft XP system is running as a virtual machine, you will need to check the same kind of configuration (basically)  on the XP system because XP is operating independently of the Linux host system.  Note that the configuration files will be located in a different directory on XP   than on a  normal Linux system.

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Has MSFT done anything with XP Lately?

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