Cyberespionage or also known as cyber spying can be described as the act of stealing information (secret, classified in nature) stored in digital format or computers or IT network - by the use of cracking techniques and malicious software including Trojan horses and spyware.Cyber spying typically involves the use of such access to secrets and classified information or control of individual computers or whole networks for a strategic advantage and for psychological, political and physical subversion activities and sabotage.

These activities are typically illegal in the victim country while fully supported by the highest level of government in the aggressor country. The ethical situation likewise depends on one's viewpoint, particularly one's opinion of the governments involved.

In response to reports of cyber spying by China against the United States, Amitai Etzioni of the Institute for Communitarian Policy Studies has suggested that China and the United States should agree to a policy of mutually assured restraint with respect to cyberspace. This would involve allowing both states to take the measures they deem necessary for their self-defense while simultaneously agreeing to refrain from taking offensive steps or engaging in cyber espionage; it would also entail vetting these commitments.