• Each of browser primary folders use an indexing technique to maintain information. Index information is contained in Index.dat files. Every browser places index.dat files differently. 
• In Internet Explorer there are three index.dat files residing in the following  locations: Cookies\index.dat, History\History.IE5\index.dat, Temporary Internet Files\Content.IE5\index.dat, hence each of Internet Explorer's primary folders  (directories) - Cache, Cookies and History use the information of index.dat. 
• Your Internet activities, the places you have visited, are logged into index.dat files and can be read by anyone. Index.dat keep basically a copy of whatever there is in browser primary folders and continue keeping those records after you have deleted the contents of those folders. 
• Index.dat files can be very hard to find and erase. If you are in Windows, even with "Show hidden files and folders" enabled, Index.dat are not always visible and cannot be found if you do a search for these files. The reason that Index.dat are so invisible is that they are not just hidden, they have been designated as "system" files, Index.dat effectively cloaked from casual searches. 
• It's necessary to restart your PC in order to clean-up Index.dat files. You can not delete Index.dat files when Windows is running, as soon as Windows starts, clean index.dat files will be created, ready to record your steps. 
• The size of empty index.dat file is 16 Kb, of clean cache index.dat file is 32 KB. Index.dat, that contains the information is large. 

Antispy Pro overwrites all index.dat files so that no one can see useful information from index.dat files.

AntiSpy Pro is designed to give even more control over cleaning process.