Shin Bet considered him its most valuable source within the Hamas leadership: The information Yousef supplied prevented dozens of suicide attacks and assassinations of Israelis, exposed numerous Hamas cells, and assisted Israel in hunting down many militants, including the incarceration of his own father, a Hamas leader, Sheikh Hassan Yousef.
Shin Bet menganggapnya sebagai sumber paling berharga dari para pemimpin Hamas: informasi Yousef menghindarkan serangan bunuh diri dan pembunuhan terhadap Israel, membongkat sejumlah sel Hamas, dan membantu Israel memburu beberapa militan, termasuk ayahnya sendiri, pemimpin Hamas Sheikh Hassan Yousef.