The science fiction novel The Three-Body Problem provides an excellent example.

By capturing the Earth rebels and obtaining their communication records with the Trisolarans, humanity gained two crucial pieces of intelligence:

The Trisolarans use "Sophons" for omnipresent surveillance, monitoring human activities in real-time.

The Trisolarans fear an ordinary man named Luo Ji and have repeatedly sent Earth rebels to assassinate him.

These two pieces of intelligence directly influenced humanity's subsequent strategic deployments, demonstrating the importance of obtaining enemy intelligence from the actions of traitors.

How an alien civilization can effectively attack another civilization.
The author, through the perspective of the Trisolarans, explains an important concept: fundamental science is crucial for the development of civilizations, and breakthroughs in fundamental science can change the fate of a civilization. 

The Trisolarans choose to attack humanity's fundamental science, particularly theoretical physics, in order to block the development of Earth’s civilization, as they believe that theoretical physics is key to humanity's understanding of the nature of the universe. The author uses particle colliders as an example to illustrate that colliders are essential for studying the nature of matter; they can help humanity understand the microscopic world, thereby driving technological advancement.

Deep thinking from:

Ye Wenjie, due to her personal experiences, became despairing of humanity and sent a signal to the universe, exposing Earth's location and inviting the invasion of the Trisolarans.

Trisolaran 1379, who was also disillusioned, responded to Ye Wenjie's signal, going against the collective interests of the Trisolaran world and bringing disaster to their civilization.

These two ordinary individuals inadvertently changed the fate of two civilizations.

Story About "The Three-Body Problem : Remembrance of Earth's Past"

The novel, set against the backdrop of the Cultural Revolution, tells the story of how Earth civilization came into contact with an alien civilization called "Trisolaris" and eventually led to the Trisolaran invasion of Earth.