Biography
Known:Unknown was an alias used on Moving Shadow for a series of remixes by well-known, but anonymous Drum and bass artists. The only release was a remix of Drum Trip. The "Chaos Edit" is actually by artist Dom & Roland.
Most people tag these two tracks as "Known Unknown" because on Windows you can't have a ':' in the file name. But, it clearly says "Known:Unknown" on the label.
Biography text from Last.fm, available under CC BY-SA.