Answer: secret gathering of information
Step-by-step explanation:
Clandestine information gathering refers to gathering information in a secret way such that the people the information is being gathered on (and indeed the rest of the public) do not know that they are the subject of such an operation.
This is the main job of intelligence agencies run by the world's governments. In gathering information in secret, they hope to protect the nation from attack by acting to stop the attack before it happens by virtue of possessing that secret information.