How would they know it’s their own government? If the NSA were in the habit of leaving calling cards, then sure some info-sec people might keep quiet out of pat

How would they know it’s their own government? If the NSA were in the habit of leaving calling cards, then sure some info-sec people might keep quiet out of patriotism, but others would be screaming from the rooftops about proof of conspiracy. More likely, as the author mentions, the NSA disguises its attacks as less sophisticated than they really are.