Serious privacy problems in Windows Media Player for Windows XP

by Richard M. Smith
February 20, 2002


I found a number of serious privacy problems with Microsoft's Windows Media Player (WMP) for Windows XP. A number of design choices were made in WMP which allow Microsoft to individually track what DVD movies consumers are watching on their Windows PC. These problems which introduced in version 8 of WMP which ships preinstalled on all Windows XP systems.

In particular, the privacy problems with WMP version 8 are:

Technical Details

When a DVD movie is played by the WMP, one of the first thing that WMP does is to query via the Internet a Microsoft server for information about the DVD. The query is made using the standard HTTP protocol that is also used by Web browsers like Internet Explorer or Netscape Navigator.

Using a packet sniffer I was able to observe WMP making these queries to a Microsoft server each time a new DVD movie was played. The packet sniffer also showed the movie information which was returned to WMP by the Microsoft servers.

The first HTTP GET request sent by WMP identified the movie being played. For example, an HTTP GET request is made for this URL for the "Dr. Strangelove" DVD: cd=1E+96+1B1E+30D9+42D8+5D61+783E+9083+C49C+F0C8+1151E+13CF9+ 15812+16C5D+1A04F+1BF2D+1ECB7+212E1+22E48+25724+27E9D+2A91A+ 2D0E6+2F451+38367+3CF64+4A4D6+4C001+4D517+4E51B+4FDBC+51F74
The hex numbers at the end of the URL are an electronic fingerprint for the DVD table of contents which uniquely identify the "Dr. Strangelove" DVD.

This URL is sent to, Microsoft's Web site dedicated to the WMP software.

The HTTP GET request also included a ID number in cookie which uniquely identifies my WMP player. Here's what this cookie looks like:

By default, this cookie is anonymous. That is, no personal information is associated with the cookie value. However, if a person signs up for the Windows Media newsletter, their email address will be associated with their cookie. For example, when I signed for the Windows Media newsletter, the following URL was sent to Microsoft servers:
The same cookie value will be sent back to Microsoft servers when signing up for the newsletter and when a DVD moive is played. In addition, using various well-known "cookie synch" tricks, an email address can be associated with a cookie value at any time.

Also when subscribing to the Windows Media newsletter, I was encouraged by an email message from the Microsoft newsletter department to create a Passport account based on my email address. In theory, yet more personal information from Passport could be matched with what DVD movies I have watched. There is no evidence however that Microsoft is making this connection.

The cookie was assigned to my computer the first time I ran WMP. The lifetime of the cookie was set to about 18 months. This cookie gives Microsoft the ability to track the DVD movies that I watch on my computer.

After a series of redirects from the WindowsMedia.Com server, information about the "Dr. Strangelove" movie was returned in this XML file:
WMP extracted movie information from this file and then added this information to a database file, named wmplibrary_v_0_12.db, which is located on my hard disk in the directory " C:\Documents and Settings\All Users\Application Data\Microsoft\Media Index". I didn't see any method of removing movie information from this file, so it appears to me that the file keeps a complete record of all movies watched that have ever been watched on my computer.

Because as of Feb. 14, 2002 the Windows Media privacy policy is silent about what is done with DVD information sent to Microsoft servers by the WMP software, we can only speculate what Microsoft is doing with the information. Here are some possibilities:

Note: The Video Privacy Protection Act of the United States prevents video rental stores from using movie titles for direct marketing purposes. The letter of this law does not a pply to Microsoft because they are not a video rental store. However, clearly the spirit of the law is that companies should not be using movie title information for marketing purposes.


I believe that the Microsoft should remove the DVD movie information feature from WMP version 8 altogether. The value of feature seems very small given that almost all DVD movies include a built-in chapter guide. In addition, the Microsoft movie information feature is not available when DVD movies are shown in full-screen which is how DVD are typically watched.

If Microsoft feels that this feature is important to leave in WMP, then I think it should be turned off by default. The feature can be made privacy-friendly very easily, by having WMP never send in cookie information with movie title requests. This change will prevent Microsoft from tracking individual movie viewing choices.

Vendor Response

Click here for the response from the Windows Digital Media Division of Microsoft Corporation.


Thanks to Ian Hopper of the Associated Press for bringing this issue to the attention of the author.


  • Digital Media in Windows XP

  • Media Player for Windows XP Privacy Statement

  • The RealJukeBox monitoring system

  • TiVo's Data Collection and Privacy Practices

  • Internet Explorer SuperCookies bypass P3P and cookie controls

  • Video Privacy Protection Act

  • Bill Gate's memo on Trustworthy computing memo