able to carry on with activities inside sony's network for so long without being spotted. moving possibly terabytes of data without anyone noticing requires skill. opening documents all over the place in order to download them and have no one notice requires quite a bit of skill. >> reporter: they didn't have that, even recently? >> that's right. earlier this year there was no sign of that level of skill. >> reporter: he believes kim jong-un's regime may have outsourced some of the sony hack but to whom? >> i think most likely this was hacking talent that volunteered to help them or criminals that they hired or someone inside of sony who provided them with all kinds of inside access. >> reporter: u.s. investigators have evidence that hackers stole the computer credentials of a sony system administrator to get inside access but could another government have helped north korea? one analyst says another u.s. enemy may be involved. >> there are signs that suggest