By Carl Tenning

Tacoma Open Group For Microcomputers

[This article applies to Windows 98 and ME]

Everyone has probably received those annoying pop-up windows. Note that pop-up windows sometimes contain spyware.

Pop-up messages and the spyware contained with the pop-up window can be blocked using the HOSTS file. The HOSTS file (with no extension) is located in the Windows Directory. If it does not exist on your computer, there is probably a file named "HOSTS.SAM". The file "HOSTS.SAM" is a sample file showing the structure of the HOSTS file.

The intended function of the HOSTS file is to speed up internet access for finding a site. Each site on the internet had a four-part numerical IP address. Normally you access an internet site by typing something like "http://www.somewhere.com" into your browser. However, your computer must convert this host name to the corresponding numerical IP address. The first place it looks is the HOSTS file. If the numerical IP address is there, it quickly connects you to that address. But if the address is not there, then it must go to a service called DNS to retrieve the numerical IP address. So then, the HOSTS file contains the mappings of IP addresses to host names. Each entry must be kept on an individual line. The IP address is placed in the first column followed by at least one space, then the corresponding host name. Here is an example:

127.0.0.1 localhost

In this example, "127.0.0.1" is the network location of your own computer.

To trick your browser into not receiving pop-up messages, you can enter your own IP address for the pop-up host name. Here is an example:

127.0.0.1 ad.doubleclick.net

So instead of going to the DNS service to find the true IP address of "ad.doubleclick.com", it finds it in the HOSTS file as your own computer. But since your own computer does not actually have that host, a blank pop-up window appears. Note that this technique also blocks any spyware the ad might contain.

There are several web sites that publish lists of pop-up host names that you can copy and past into your own HOSTS file. Just remember that the HOSTS file is a pure text file and should be edited with Notepad, WordPad, or DOS Edit. Another thing to remember is to not try editing the HOSTS file while you are connected to the internet, as it might lock up your computer (it did on mine). You probably have to reboot to make your new HOSTS file effective.

Here are some web sites that publish entries for the HOSTS file for the purpose of blocking pop-up messages: