In most of the latest high-profile breaches, the threat was found only after the forensics team came into the picture. "Existing network security mechanisms remained clueless,"
However, search hard enough on any network and I'll bet you could find some speculative evidence of unauthorised access or malware that really amount to very little of interest. Is there sometimes an over analysis of forensic results when it comes to IT systems? I've seen plenty of vulnerability test reports that over-egg benign issues into something far more serious than they really are.
I'll be interested to see where this story goes.