Trilight Zone

[digital8]

What is the index.dat file?
The index.dat file is used by Microsoft Internet Explorer 4, 5 and 6 to record information about Internet sites that have been visited and details of cookies being stored on your computer.
Whenever you visit a website on the Internet; the address, time of visit, images, scripts, tracking cookies and web page contents are saved to your hard drive. The primary reason Internet Explorer does this is to allow quicker access to the site if you revisit again because the contents can be opened from your computer disk drive rather than downloaded over the Internet a second time. Information about these cache files, cookies and where Internet Explorer can find them on your hard drive is stored in the hidden index.dat file.

How does the index.dat file compromise privacy?
Internet Explorer gives you the ability to remove and clear some of the information that is has saved to your computer after visiting sites. But unfortunately it does not clean all of it, including the index.dat file. Therefore it is possible for someone with the right tools to see which sites have been visited and which files have been downloaded simply by viewing the contents of the index.dat file stored on your computer.

With the increasing threat of spyware and malicious web-sites redirecting you to illegal or pornographic material this lack-of privacy means that these sites will be stored and viewable in the index.dat even if they were visited unintentionally.

How can I delete index.dat?
Unfortunately index.dat is not easily deleted, even once the hidden file is found you can not simple drop it on the Recycle Bin to remove it. Index.dat is what is known as a “locked file” which means it is open all the time and can not be deleted using conventional methods.

It is possible (but complicated) to delete the index.dat by rebooting your computer and using a MS-DOS boot disk, normally you can then access the drive and manually locate the file which is hidden is several locations. This is method is complicated and error-prone as Internet Explorer usually stores more than one copy of index.dat and finding them all when they are located in hidden directories can be difficult. There is one other major problem with this method, due to the ability to undelete the index.dat file (see the sidebar for information on a solution).