Definitions of infiltrate:

• verb:   enter a group or organization in order to spy on the members

  Example: "The student organization was infiltrated by a traitor"

• verb:   pass through an enemy-line; in a military conflict
• verb:   pass into or through by filtering or permeating

  Example: "The substance infiltrated the material"

• verb:   cause (a liquid) to enter by penetrating the interstices