The loophole in the Windows Media DRM process allows companies to create media files and link them to adware. When you normally download a protected Windows Media file, you also receive a license that lets you play it. If however Windows Media Player cannot find a valid license on your PC, it checks in with a remote system running Microsofts Windows Media DRM Server.

You should rarely see that happen. Some files, however are set up to ask you for information before playing. They do this by displaying a URL in a dialog box labeled License Acquisition. Normally that dialog box is used to check for a user name or offer a chance to purchase the file thats being played. In a legitimate DRM-encrypted file the author may let you play it a few times, then bring up a window asking if you want to buy it.

Since the license dialog box is in essense an Internet Explorer window, it will display whatever is on the page it points to, in the cases that have been seen of this these trojaned Windows Media files, they all point to servers that load up unwanted ads, including windows that attempt install adware onto your PC surreptitiously, including adding items to your browsers Favorites list, attempting to change your home page and installing viral adware such as the 180search Assistant.

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