Index.dat Files
Ah, the index.dat files. What are they? What purpose do they serve?
Simple as this: the index.dat files are used by Internet Explorer mainly in the Temporary Internet Files folder and the History folder.
In the Temporary Internet Files folder, Internet Explorer uses the index.dat file to keep track of each web site you visit and each file associated with each web site. That way, when it needs to retrived cached pages, it can do so by reading the information in the index.dat file for a particular site.
A single entry in the index.dat file looks like this when viewed in a plain text editor:
~U:username
URL . pw—.RÆÁ. c. ` h . ..¤ A. ´ h,ú.. h,ú.
http://www.tweakie.com/default.htm default[1].htm HTTP/1.1 200 OK
Content-type: text/html
Page-Completion-Status: Normal
Page-Completion-Status: Normal
As you can see, even with some of the gibberish, it is quite easy to extract the site and page that was viewed. In most cases, this can be done for every page you have ever visited. In the best case, for you, this can be done for only the pages you have visited over the last 6 months or so.
How can this be? Why would Internet Explorer need this data after 6 months or more? Is it still there if I delete my Temporary Internet Files via Internet Explorer?
The simple answers are: 1) Who knows?, 2) Due to page caching and 3) Yes!
The complete answers are:
1) We still don't know exactly
2) Since Internet Explorer caches web pages so they can be displayed more quickly without the need to download them again and because page designers can set their own expiration dates to tell Internet Explorer how often it should re-download the entire page, this information is retained.
3) Yes, the information in the index.dat file remains even if the files for ANY given site are deleted. Why? We don't know. Ask Microsoft, they won't tell you and have never explained it when the media has spoken to us and then to them. The fact of the matter is that if you think you have deleted all traces of web sites you have visited by deleting the Temporary Internet Files, think again.
Due to our knowledge of these files, we have been contracted, on occasion, to retrieve information from them by companies seeking the knowledge of what their employees have been viewing on company systems even after the Temporary Internet Files are deleted. In one case, a worker was fired from a school for viewing inappropriate material and, in another case, a worker was brought up on insider trading charges filed with the SEC due to online trading he was doing at his company.
Keep in mind, that only someone with direct access to your computer can gain access to these files.
No web sites you need to hide you say? Well, there is also a performance consideration. Each time Internet Explorer loads a page, it scans the index.dat file. This file, since it is never emptied, keeps growing larger and larger until it is many megabytes in size. Logic says that the larger the file, the longer it takes to read it. Microsoft seems to have alleviated most crashes in Internet Explorer that were occurring as the index.dat file grew too large, but Internet Explorer can still drag a bit when the file gets to big.
In the History folder, the index.dat file is used in very much the same way, except that it is used to track links you have clicked on so Internet Explorer can display them as visited. Also, there is one main index.dat file as well as one in each of the daily folders for each day's History.
The same problems are inherent to these index.dat files as the one in the Temporary Internet Files
Maybe you can help me. I moved from one PC to another. I'd like to move the bookmarks in IE from my original PC to my new one. What file are they in?
Are there any other "persistent" files that we should know about that can or should be deleted. Windows ME user here.
