Your password search for F source will return better results if you exclude words in your search such as: password, unlock, crack, cracker, remover, hack, extract, open, recovery, winrar, rar, winzip, zip, etc.

You may also search for the URL of where the file that is password protected is located. Most commonly password protected files such as F source are downloaded from services such as Rapidshare.com, Megaupload.com, Depositfiles.com, Easy-share.com, Hotfile.com and Uploading.com.

If a file has been downloaded via torrent you may search for the filename of the particular torrent file that is password protected.