infiltration

These layers can block the downward movement of water in places, slowing infiltration to deeper levels.

His letter began: "The infiltration of the social work profession by paedophiles appears to be an extensive and serious problem..."

The latest hack, announced on Monday, targeted the US Department of the Treasury, which called the infiltration a "major incident".

So, possible infiltration strategies include broadcasting messages through loudspeakers or using drones to drop leaflets.

The ruling from the IPT is the second in days, underlining the scale of suspected Chinese state infiltration in the British state.