noun. One who infiltrates an organization or territory; an undercover or covert agent.

noun. someone who takes up a position surreptitiously for the purpose of espionage

noun. an intruder (as troops) with hostile intent

"The order changes the definition of the term infiltrator, deeming anyone who lacks an Israeli-issued permit to be an infiltrator subject to automatic deportation or a lengthy jail sentence."

interloper  intruder  spy  trespasser  undercover agent  

Myrmidon  acquirer  acquirers  blockade-runner  briber  

informant  narc  plant  provocateur  spy