the.com/infiltration
The art of getting all the way inside before anyone asks for your ID.
means The act of slowly entering or seeping into a place, group, or system, usually quietly and often without permission.
from From Latin filtrum, a felt strainer—the same root as filter. To infiltrate is to seep through like liquid through fabric, drop by patient drop.
SpycraftCold War term of art for planting moles inside organizations.
HydrologyDescribes water soaking into soil, not running off.
MedicineFluid or cells leaking into tissue where they don't belong.