brian todd here watching what's going on. >> we are getting new information on the sophisticated methods isis has for hiding all of its communications. we're told investigators have had a difficult time finding electronic traces that these paris attackers left behind. officials attempts to break the isis codes are starting to become a modern day version of the movie "the imitation game." >> reporter: they planned coordinated, complex attack and there's new information tonight on tight operational security and communication among these terrorists. investigators have found evidence operatives tied to the paris attackers frequently changed cell don'ts, switched cars, even searched for possible listening devices. according to counterterrorism and intelligence officials, there's evidence that they used encryption. >> may be using encrypted messaging apps they do a good job of hiding whatever you're saying from being intercepted from a government. >> reporter: conversations chopped up into a jumble by