C:\WINDOWS\system32\drivers\etc\hosts file in Windows XP

What is the C:\WINDOWS\system32\drivers\etc\hosts file for on XP?
Sưu tầm: http://answers.yahoo.com/question/index?qid=20080309160143AAwJUpT
http://en.wikipedia.org/wiki/Hosts_file
http://www.mvps.org/winhelp2002/hosts.htm

It's your Hosts file. Think of it as a Rolodex for your computer. Its where a computer looks first to translate the URL of a website into a numerical IP address that it can actually use.

Lấy ví dụ yahoo.com là http://66.94.234.13

Dùng Hosts file có thể tăng tốc một chút, nhưng hiện nay gần như không còn được dùng như mục đích ban đầu của nó.

Hiện nay, Hosts file được dùng chủ yếu để khóa truy nhập các websites không mong muốn. Chẳng hạn như ad-servers và các trang được biết là có malicious code (viruses...). Bằng cách ấn định một địa chỉ IP address của 127.0.0.1 cho bất kỳ trang nào không mong muốn. 127.0.0.1 being ones own computer (localhost) which effectively blocks access to the site!

There are several readily availible Hosts file block lists that are used to totally block access to bad, suspect and annoying sites.

MVPS has an excellent HOSTS file block list,
"Bạn có thể tùy chỉnh HOSTS file để chặn ads-quảng cáo, 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." About 30000 sites, ad-servers etc are blocked!
free at: http://www.mvps.org/winhelp2002/hosts.htm

The use of a custom Hosts file is a nice extra layer of security. After all, a website can't infect you if you can not access it now, can it?

What it does ...
The Hosts file chứa the mappings của địa chỉ IP tới tên của host. File này được load vào bộ nhớ - memory (cache) ở startup, sau đó Windows kiểm tra the Hosts file trước khi nó truy vấn bất kỳ DNS servers nào, 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 (your) 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 127.0.0.1 ad.doubleclick.net 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) *.doubleclick.net is included in the "Restricted Zone".

More Examples
AdTech | BridgeTrack | Honesty | Mgnetwork | ValueClick | 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" for the 2nd time ...

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. (597 kb) (opens in browser) Note: The text version also makes a terrific reference for determining possible unwanted sites Download: hosts.zip [right-click - Select: Save Target As] [Updated February-11-2009]

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 " width="22" align="baseline" border="0" height="17"> 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 "hosts.zip")
MD5: 07ddea0cb7d2c5083775cf122ebb20c4 SHA-1: 8c504a97dd3ae52282d3ba4c3a8a8596a352d257
(created by File Checksum Integrity Verifier) To view Checksum for this download " width="22" align="baseline" border="0" height="17"> [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	=	C:\WINDOWS\SYSTEM32\DRIVERS\ETC
Windows XP	=	C:\WINDOWS\SYSTEM32\DRIVERS\ETC
Windows 2K	=	C:\WINNT\SYSTEM32\DRIVERS\ETC
Win 98/ME	=	C:\WINDOWS

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 127.0.0.1 is the location of your computer, so when the entry (example) "ad.doubleclick.net" is requested your computer thinks 127.0.0.1 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 (or Disabled) you can see that the above "Service" is not needed (after a little browsing - when set to Manual) 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 work 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
How To Uninstall the MVPS HOSTS file

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

• You cannot modify the Hosts file in Windows Vista
• Options for Using the Ipconfig Diagnostic Utility (XP)
• WinME users - Start | Run (type) "winipcfg" (no quotes)
• "The Page Cannot Be Displayed" Error Message (XP) [more info]
• Error Message: The Page Cannot Be Displayed (98/ME)
• "The Page Cannot Be Displayed" Error Message (2K)
• Repairs Winsock 2 settings (usually spyware related)
• How to Reset Internet Protocol (TCP/IP) in Windows XP
• How to Troubleshoot TCP/IP Connectivity with Windows XP