Google's Desktop Search, which runs continuously, creates a copy (or Cache) that lingers after the original is deleted. This makes it difficult -- to say the least -- to manage sensitive information. In addition, Google by default indexes secure Web pages. So if you shop online or manage your stocks at a Web address that begins with HTTPS:, rather than HTTP:, those pages are also saved. These pages often contain confidential information, such as credit card numbers. Further, it indexes your temporary Internet files and saves AOL Instant Messages. Google can also index password-protected Word or Excel files. And you don't need the password to view the cached file that appears on the search results listing.
Fortunately, the latest version of Google Desktop Search is equipped with better privacy options. You can opt not to index certain file types, deselect secure Web pages, exclude file folders and specific Web sites from the search index.
In terms of security and privacy, Yahoo! desktop search program, based on X1 technology is better as they don't retain copies of deleted files or index temporary Internet files. Unfortunately, it does index files in password-protected mail folders. [Via]