Final answer:
The provided excerpt does not detail the specific private sector entities contacted by Cliff Stoll during his investigation in 'The Cuckoo's Egg'.
Step-by-step explanation:
Cliff Stoll's book "The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage" is a classic tale of real-life cyber investigation. In the quest to identify computer intruders, Cliff Stoll did not act alone; he leveraged the help of various private sector entities during his investigation. However, the excerpt provided does not give details about the specific private sector entities that Cliff Stoll contacted. To properly address the question posed, access to the content of Cliff's book or other sources would be necessary to provide factual information regarding the private entities involved in assisting him with the forensic analysis.
The content provided discusses historical espionage cases and the development of technology during the Cold War period, which is contextually relevant to understanding the environment in which computer forensics began to evolve but does not directly answer the student's question about Cliff Stoll's interactions with private sector entities.