Blocking Unwanted Parasites with a Hosts File


Blocking Unwanted Parasites with a Hosts File

What it does …
The Hosts file contains the mappings of IP addresses to host names. This file is loaded into memory (cache) at startup, then Windows checks the Hosts file before it queries any DNS servers, which enables it to override addresses in the DNS. This prevents access to the listed sites by redirecting any connection attempts back to the local machine. Another feature of the HOSTS file is its ability to block other applications from connecting to the Internet, providing the entry exists.

You can use a HOSTS file to block ads, banners, 3rd party Cookies, 3rd party page counters, web bugs, and even most hijackers. This is accomplished by blocking the connection(s) that supplies these little gems.

Example – the following entry blocks all files supplied by that DoubleClick Server to the web page you are viewing. This also prevents the server from tracking your movements. Why? … because in certain cases “Ad Servers” like Doubleclick (and many others) will try to open a separate connection on the webpage you are viewing.

For XP SP2 users you should see a Security Center prompt about allowing this connection. [screenshot]
Simply click No and continue. Yes the prompts can be annoying but at least you’ll know, however you should not see these prompts if these entries are included in the HOSTS file.
Note: this prompt only occurs if (example) * is included in the “Restricted Zone“.
More Examples
AdTechBridgeTrackHonestyMgnetworkValueClick | Google AdSense | Atdmt | Atdmt
Now here is a 3rd party ad server opening a connection to another 3rd party ad server – Ad-Flow
More 3rd parties opening other 3rd parties: Overture | Overture | Directtrack | Directtrack | RealMedia
Note: By placing these type sites in the Restricted Zone this also cures most “Back Button” issues.
Now includes most major parasites, hijackers and unwanted Adware/Spyware programs!
Proudly now the #1 rated HOSTS file on the Internet!  – Google | MSN | Yahoo | AltaVista
Now regularly featured on the Kim Komando Radio Show
The MVPS HOSTS file has been selected by Pricelessware as “the best of the best in Freeware

In many cases using a well designed HOSTS file can speed the loading of web pages by not having to wait for these ads, annoying banners, hit counters, etc. to load. This also helps to protect your Privacy and Security by blocking sites that may track your viewing habits, also known as  “click-thru tracking” or Data Miners. Simply using a HOSTS file is not a cure-all against all the dangers on the Internet, but it does provide another very effective “Layer of Protection”.

Editors Note: As time has progressed the focus of this project has changed from just blocking ads/banners to protecting the user from the many parasites that now exist on the Internet. It doesn’t serve much purpose if you block the ad banner from displaying as most other HOSTS files do, but get hijacked by a parasite from an evil exploit or download contained on the web site. The object is to surf faster while preserving your Safety, Security and Privacy. [more info]

To view the HOSTS file in plain text form. (633 kb) (opens in IE)
Note: The text version also makes a terrific reference for determining possible unwanted sites
Download: [right-click – Select: Save Target As] [Updated 12-10-07]

This download includes a simple batch file (mvps.bat) that will rename the existing HOSTS file to HOSTS.MVP then copy the included updated HOSTS file to the proper location. For more information please see the readme.txt included in the download.

Important! Windows Vista requires special instructions Not here - over there > see here

When you run the (mvps.bat) batch file XP users may see a prompt, simply click Run and continue. Once updated you should see another prompt that the task was completed. Some users may see a pop-up from certain Security programs about changes to the HOSTS file. Allow the change … however if you see this pop-up at any other time … investigate.
Download Information: (checksum info is on the HOSTS file not the “”)
: 760ea5bd4996887949190ea60688377c SHA-1: 01c231d891f22d0a531d3177116a3f7abfdc323a
(created by File Checksum Integrity Verifier) To view Checksum for this download  Not here - over there > [click here]
Manual Method – Unzip in a “temp” folder and place in the appropriate installed location:

  • If you are having trouble downloading or extracting the HOSTS file [click here]
    Note: the below locations are for the typical default paths, edit as needed.

Windows Vista

Windows XP

Windows 2K

Win 98/ME

There is no need to turn on, adjust or change any settings with the exception of the DNS Client service (see below). Windows automatically looks for the existence of a HOSTS file and if found, checks the HOSTS file first for entries to the web page you just requested. The is the location of your computer, so when the entry (example) “” is requested your computer thinks is the location of the file. When this file is not located it skips onto the next file and thus the ad server is blocked from loading the banner, Cookie, or some unscrupulous ActiveX, or javascript file.

In case you’re wondering … this all happens in microseconds, which is much faster than trying to fetch a file from half way around the world. Another great feature of the HOSTS file is that it is a two-way file, meaning if some parasite does get into your system (usually bundled with other products) the culprit can not get out (call home) as long as the necessary entries exist. This is why it’s important to keep your HOSTS file up to Date. Subscribe to a secure mailing list

Editors Note: in most cases a large HOSTS file (over 135 kb) tends to slow down the machine. This only occurs in W2000/XP/Vista. Windows 98 and ME are not affected.

To resolve this issue (manually) open the “Services Editor

  • Start | Run (type) “services.msc” (no quotes)
  • Scroll down to “DNS Client“, Right-click and select: Properties
  • Click the drop-down arrow for “Startup type
  • Select: Manual, or Disabled (recommended) click Apply/Ok and restart. [more info]

When set to Manual you can see that the above “Service” is not needed (after a little browsing) by opening the Services Editor again, scroll down to DNS Client and check the “Status” column. It should be blank, if it was needed it would show “Started” in that column. There are several Utilities that can reset the DNS Client for you … [more info]

Editors Note: The above instructions are intended for a single (home-user) PC. If your machine is part of a “Domain”, check with your IT Dept. before applying this work-around. This especially applies to Laptop users who travel or bring their machines home. Make sure to reset the Service (if needed) prior to connecting (reboot required) to your work Domain …
JBF sends along this Tip: IPCOP running a DHCP server needs the local PC DNS Client enabled to function.

Reset the DNS Client with a simple batch file (submitted by: Ronny Ong – 2K/XP only)

DnsManual.bat (resets the DNS Client to Manual) [right-click and select: Save Target As]
DnsDisabled.bat (resets the DNS Client to Disabled) [right-click and select: Save Target As]
To use: double-click on the downloaded file and reboot that’s it …

For all other Questions, Issues and Solutions – see: The HOSTS File FAQ
For detailed Download and Extract Instructions – see: Download Help

Related Utilities

  • SpywareBlaster can encrypt and create a backups of your HOSTS file.
  • WinPatrol will allow you to lock your HOSTS file and will monitor changes.
  • ZoneAlarm Pro and Security Suite users have a “Lock Hosts” file option.
    However this requires special instructions to edit or update the HOSTS file.

HostsMan is a freeware application that lets you manage your Hosts file.
Includes an option to turn off the unneeded DNS Client Service.
This also has an option to update the existing HOSTS file when needed.
Important! – make sure you select: Default action – Overwrite
Use the Server option to replace the Action Cancelled message.

Windows Vista users … once installed right-click on “hm.exe” and select: Properties
Click the Compatibility tab and select: “Run as Administrator” [screenshot]

Rename the HOSTS file on the fly … a simple one click batch file. (Win9x/XP)

HostsXpert is a terrific multi-function Hosts File Manager [screenshot] (XP only)
Note: no install required, it runs from anywhere … when updating the HOSTS file make sure to use the Replace option, rather than Merge [screenshot]

Homer is a LocalHost webserver used to replace the Action Cancelled message.
Download a custom image for use in Homer.
Simply save (Save Target As) blocked.gif (2 kb) to the “\Homer\Homer\images\” folder.

Various Troubleshooting Articles


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