Wikipedia
Mista'arvim (, literally Arabized; , Mustaʿribīn), also spelled as mistaravim, is the name given to counter-terrorism units of the Israel Defense Forces, Israel Border Police and Israel Police who operate undercover. Such units are specifically trained to assimilate among the local Arab population. They are commonly tasked with performing intelligence gathering, law enforcement, hostage rescue missions and counter-terrorist operations, that uses disguise and surprise as their main weapons.
The name is derived from the Arabic "Musta'arabi", meaning "those who live among the Arabs", which refers to the Musta'arabi Jews - Arabic-speaking Jews who lived in the Middle East since the beginning of the Arab rule in the 7th century, prior to the arrival of Ladino-speaking Sephardic Jews following their expulsion from Spain in 1492.