The hosts file is, in fact, a single text file, which you
can edit with notepad if you wish.
It has a single line in it for a given host--of the form
ip address host, usually with a tab in between so you get
a nice neat list.
The original purpose of the hosts file was name resolution-
-it is tried FIRST in an attempt to reach a given host.
However, this mechanism has been used more recently for a
completely different purpose--to PREVENT reaching a given
host.
If you are seeing a long list of items starting with
127.0.0.1 and ending with the name of some site that you
are pretty sure you shouldn't be going near--you are
seeing the result of using some other antispyware program--
perhaps Spybot Search & Destroy, on your system.
If you have a line that says 127.0.0.1 egg.foo.com--this
works as follows:
You type egg.foo.com into your browser, or it is part of
an innocent looking link that you click on, and the hosts
file redirects that access to your own machine--and
nothing happens. You can't go there.
So--these lines are meant to be Good--to be protective.
The file can and is being used in the opposite way as
well: A number of viruses plug the sites of major
antivirus vendors into the hosts file to prevent the user
from updating their definitions, or getting help via an
online scan.
Additionally, there are some helpful folks around the 'net
who publish hosts files which you can import into your own
file to keep safe. There are at least 3 or four of these
files which include this line:
127.0.0.1 spynet.com
Spynet.com happens to be where Microsoft Antispyware gets
its definitions.
So if you've loaded one of these helpful files into your
system, you won't be able to get new definitions.
Fortunately, these are fairly out of the way sites--not
the main ones that folks go to for this information.
So--the hosts file is a two-edged sword. If you have
hundreds of entries, how do you spot whether
www.symantec.com is in there along with egg.foo.com?
So---some of us here prefer to keep the hosts file empty--
one entry (127.0.0.1 localhost)--so that we can see what
is happening in it.
The hosts file lives in c:\windows\system32
\drivers\etc\hosts on many systems. It can be edited
with notepad, and mine looks like this:
-------------------------------
# Copyright (c) 1993-1999 Microsoft Corp.
# This is a sample HOSTS file used by Microsoft TCP/IP for
Windows.
# 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
-----------------------------
The pound sign starts a comment.
This is a stock default hosts file and is all that is
needed--in fact, just the final line is all that is needed.
On larger corporate networks, there may well be real
entries in the hosts file that are important to the
function of the network--but this isn't true for the
average home user.
