>> bits and pieces of things will be taken from many different sources, different laptops, different computer systems that have been compromised, but it is hard to take a lot of pieces and gel them into one comprehensive picture of what might be being built or what the designs are. >> reporter: cnn couldn't independently verify the latest report findings. several members of the defense science board we contacted declined to speak to us. u.s. defense and other officials down play the report, saying some of the information is dated, that they've taken steps to address the concerns. one saying, quote, the idea that somehow whoever the intruders were got the keys to the weapons kingdom is a stretch. but the pentagon has accused china of -- if the chinese got into parts of combat or missile defense system, how could they get past the safeguards. >> there's engineering that is done in an academic setting, at