My last blog showed how, with a few settings, you can reduce the risk of your browser being used as a vector into your computer. In the discussion following the blog, some mentioned additional tools they use to stay safe. One user, tech_ed, mentioned an option that has long been forgotten by the modern Internet, but is still a viable tool: the host file, which can reduce the amount of advertising you receive in your browser and can actually speed up your connection.
In the early stages of the Internet, the Domain Name System (DNS) did not exist; there was no Web yet. In order for computers to find each other, their operating systems provided a place where system administrators could list the names of each node on their particular networks. As the Internet grew in popularity and size, the "hosts file" became an overwhelming management task, prompting the creation of DNS.
Like many legacy features that remain in today's OSs, the hosts file is no longer used to locate nodes on the Internet. But you can use it to block certain sites that you do not want loaded in your browser.
All ad servers host their content at an address, such as: http://www.evilad.com/ad/eviladd.jpg. When your browser comes across this link, it will look for the site locally; if it is not cached, it will query DNS, which takes time and may delay loading the page.
You can use the hosts file to redirect this ad server to your local machine, whose IP address is 127.0.0.1. When your browser searches for the image from the evil ad server, it will first look in the hosts file and try to load http://127.0.0.1/ad/evilad.jpg. Since the folder and image don't exist on your computer, the image won't load, thus blocking the ad from showing in your browser.
Additionally, your hosts file can assist in blocking malicious or criminal domains and servers containing spyware, adware, and other forms of malware.
Now that you understand the hosts file, let's explore how to modify it.
Every computer has a hosts file, regardless of OS, but there are many different locations for it. Below are listed the locations for host files in the most common operating systems.
1. Windows NT/2000/XP/2003/Vista/7:
You will find it in the Registry: %SystemRoot%\system32\drivers\etc\ is the default location, which may be changed. The actual directory is determined by the Registry key: \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DataBasePath.
2. Windows 95/98/Me: %WinDir%\
3. Mac OS X:/private/etc/hosts
4. Linux, BSD-based, and other Unix-like operating systems: /etc/hosts
The hosts file can be opened in Notepad for Windows or in any text editor in Mac OS X or Linux. Once open, you can edit it to block any sites you want to avoid that may contain advertising or objectionable content.
Now before you start typing away, there are sites maintained by vigilant users that provide hosts file lists. An example of this was brought to my attention by tech_ed , who directed me to the following URL: http://www.mvps.org/winhelp2002/hosts.htm
The Webmaster of this site has hosted it for 10 years and provides a downloadable hosts file you can use in full or modify as necessary. You can copy this file into the hosts folder, restart your browser, and see how it works.
I do have a few words of caution regarding this new security tool: First, your overall browsing experience may be affected. If you like the ads and Website interactions associated with today's browsing, then this security solution may not be for you. Second, as with all security-based solutions, it may require some tweaking on your part to find the balance that works for you. Lastly, security is a marathon and not a sprint. Therefore, as ad server names change, your hosts file will need to be updated on occasion.
I would recommend that you review your hosts file on a monthly basis with the other maintenance you perform on your computer, but at least every two months. This security solution is just another way that becoming more familiar with your browser will provide you an additional resource in protecting yourself and your online identity.
