Infiltrate (verb)

1. Enter or gain access to (an organization, place, etc.) surreptitiously and gradually, esp. in order to acquire secret information.
2. Spread through or permeate (a substance, tissue, etc.) gradually.

Origin:

Early 17th century: from latin infiltrat- "soaked in", from the verb infiltrare, from in- "into" + filtrare "filter". .

Examples:

1. The spy managed to infiltrate the enemy organization.
2. Water infiltrated the cracks in the dam, causing it to fail.
3. The new management has infiltrated the company's culture.
4. The virus infiltrated the host cell.
5. The protesters infiltrated the event and caused disruptions.