Windows 2000 uses ADS to store thumbnails in image files, and to store summary information (such as title and author) in any file, without changing the main stream. With Windows XP, Microsoft realized that ADS is susceptible to loss when the files containing them are moved off NTFS volumes; thus Windows XP stores them in the main stream whenever the file format supports it. Windows Vista discontinued support for adding summary information altogether, as Microsoft decided that they are too sensitive for ADS to handle. But the use of ADS for other purposes did not stop. Service Pack 2 for Windows XP introduced the Attachment Execution Service that stores details on the origin of downloaded files in an ADS called "zone identifier", in an effort to protect users from downloaded files that may present a risk. Internet Explorer and Windows 8 extended this function through SmartScreen. Internet Explorer also uses ADS to store favicons in Internet shortcut files.