Don't let these ninja hacker posers fool you. It's a database of the thumprints of everyone who has ever used the keyboard on your computer. They're recorded by a hack of the keyboard driver that reverses the polarity of the key solenoids to detect electrostatic contact prints each time you press a key. The first virus that created thumbs.db files was called "FiNgErL4wg." All the files contain the same data, but it duplicates them in many randomly selected folders to ensure that at least one will be available when it needs to upload the database to a remote bot host over the internet, which it does several times a day.