infiltration

US /ˌɪn.fɪlˈtreɪ.ʃən/
UK /ˌɪn.fɪlˈtreɪ.ʃən/
1.

sự xâm nhập

the process of secretly becoming part of a group in order to get information or to influence the way that a group thinks or behaves:

:
Police infiltration of Greenpeace sparked the scandal.