Infiltration (noun)

1. The act of secretly entering or entering surreptitiously a place, organization or group.
2. The act of penetrating an enemy or hostile force's defense or position.

Origin:

The word "infiltration" comes from the latin word "infiltrare" meaning "to filter in."

Examples:

1. The spies used infiltration to gain access to the secret documents.
2. The police used infiltration to gather information about the criminal organization.
3. The company was concerned about infiltration by its competitors.
4. The infiltration of the enemy's position was a key part of the battle plan.
5. The enemy was able to infiltrate the camp, causing confusion and panic among the soldiers.