Among recent applicants for jobs at the CIA, a small but significant percentage had questionable connections to Islamic organizations considered hostile to the US and Israel, The Washington Post revealed on Monday.

Certain aspiring spies were found to have questionable backgrounds, and, among those, around one in five had “significant terrorist and/or hostile intelligence connections” to Hamas, Hezbollah or al-Qaeda, according to a classified budget document obtained by the American paper.

The document, the subject of a series of in-depth articles published recently by the daily, was acquired from fugitive whistleblower Edward Snowden.

A CIA official questioned on the matter told the paper that “over the last several years, a small subset of CIA’s total job applicants were flagged due to various problems or issues. During this period, one in five of that small subset were found to have significant connections to hostile intelligence services and or terrorist groups.”

The CIA was concerned enough about the risk of infiltration to set up a special program to review the security clearances of some 4,000 employees with high-level access in 2013 alone, which, according to the report.

Last week, a Washington Post article on the leaked documents indicated that the US had considered Israel a “priority target” for intelligence gathering, along with China, Russia, Iran and Cuba.