Invasion

Noun

1. A military action consisting of a large armed force of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government.
2. The entry without consent of an individual or group into an area where they are not wanted.

   "an invasion of mobile phones"

3. The spread of cancer cells, bacteria and such to the organism.
4. The breaching of the skin barrier.