What is index.dat file and how your internet privacy is affected



index.dat files expose potential privacy threat to users of a Windows computer. index.dat files are very difficult to get deleted manually because in most cases they are used and locked by Windows operating system. Even after deleting your cookies and cache, cleaning your history, index.dat files still contain records of your online and some local activities.

What is index.dat?

index.dat is a system binary file that only Microsoft Internet Explorer uses to store various information about the web pages and websites you have visited or any files you have opened by using Internet Explorer. index.dat is designed for IE internal use only. Some index.dat files are visible after you have enabled Show hidden files and folders in Folder Options. Some are hidden even though you have enabled Show hidden files and folders in Folder Options.

Many Internet users never even heard about the existence of this file. After reading this article, you should become at least aware of the potential privacy issues this file could expose you to.

What specific information does index.dat contain?

Generally, index.dat stores summary information (URL or file path, date and time, etc) about all files you have ever opened by using Internet Explorer. These include web pages, websites, local files, image files, PDF files, etc. The time frame of storing these information spans from the very first web page or file opened by IE to the most recent one visited or opened.

Since the first time your Internet Explorer was used, all the web pages visited or files opened were recorded. Does this sound scary? The first time when I scanned my index.dat files, I found 4,984 web page URLs. This check was conducted after I run the Free Internet Eraser which deleted everything except the content of index.dat files.

If a computer is shared / accessed by different users (each user has their own log in ID), index.dat exists for each user who used the computer's IE.

index.dat normally stores:

1. Web page URLs.
2. Complete URL parameters of the web page visited.
3. Count of visits to a web page.
4. Date and time a web page was visited.
5. The URL of any pictures downloaded.
6. Cookies
7. Full path to any local files opened by Internet Explorer.
8. ...

Why everyone should pay attention to index.dat

1. Because index.dat files store the web page URLs or local file paths the user visited or opened in IE, with the help of a free index.dat tool, anyone can see what web pages or files you accessed.
2. Spyware could also use information stored in index.dat files to explore your privacy.
3. If the size of index.dat files gets very large, it could adversely affect your Internet performance.

Where to find index.dat files

index.dat resides primarily in three Internet related folders / directories:

1. Temporary Internet Files: index.dat file in this directory stores almost all the website addresses of the web pages and pictures you have opened in Internet Explorer, including the locations of local files and pictures. Cleaning Temporary Internet Files would not erase the content of index.dat file. It will only remove the cached files but the web page URLs stored in index.dat are kept intact.

2. History: index.dat contains all the URLs or paths you have ever opened in Internet Explorer. Removing IE History by using IE's Clear History button won't help. It will only remove the History but not the content of index.dat file located under the History folder.

3. Cookies: index.dat contains a list of cookies placed on your computer by sites you visited. Cookies are small files placed on your computer by the websites you visited. By using cookie, the websites you visited can easily identify you when you come back to the site again. Based on what stored in your cookie, the site can track your behavior and customize the web pages you are visiting. For example, display what type of ads for you.

   The content of index.dat file in the Cookie folder is not very hard to remove. You can easily delete its content by using IE's Delete Cookies button.

On a Windows 95/98/Me computer, index.dat files reside in the following directories (examples only, not complete list):

WINDOWSCookiesindex.dat
WINDOWSHistoryindex.dat
WINDOWSTemporary Internet Filesindex.dat

On a Windows 2000/XP computer, there are several "index.dat" files in these folders (examples only, not complete list):

Documents and SettingsCookiesindex.dat
Documents and SettingsLocal SettingsHistoryHistory.IE5index.dat
Documents and SettingsLocal SettingsTemporary Internet FilesContent.IE5index.dat
Documents and SettingsLocal
Internet FilesContent.IE5index.dat

denotes Administrator, Default User, and any other specific usernames.

An empty index.dat file under Cookies and History directory is 16 KB. An empty index.dat under Temporary Internet Files directory is 32 KB.

How many index.dat files could my computer have

With the help of FREE Index Dat Spy, in my last scan of my PC I found 38 index.dat files located in various folders.

How to delete index.dat file or erase its contents

Permanently and completely removing index.dat files is not possible because it is a system file that Windows uses internally. The only way to remove them is during Windows reboot in DOS mode. Once they are used by IE, Windows places a hold on the file to prevent it from getting removed. (Note: It is possible to log in using Administrator account and remove index.dat of other users).

If Windows doesn't find index.dat files, it will always automatically create new index.dat files with empty content of size 16 KB or 32 KB.

To get to DOS on Windows 95, 98, 98SE or Windows ME, after re-start your computer, keep pressing F8. If done correctly, you will be presented with a black screen containing options. Select the option labelled "Command Prompt Only".

For Windows 2000, XP, instead pressing F8, you need to press Delete key.

If Windows doesn't find index.dat files, it will always automatically re-create new index.dat files with empty content of size 16 KB or 32 KB. Once they are used by IE, Windows places a hold on the files to prevent them from getting deleted. (Note: It is possible to log in using Administrator account and remove index.dat of other users)

The best way to remove the content of index.dat files is with the help of privacy eraser software. The good news is that you can use freeware Index.dat Suite to remove the contents of all or selected index.dat files without having to boot into DOS.


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