Amnesty International says hackers recently targeted one its staffers in a sophisticated surveillance effort by a hostile government to spy on the group’s work. The staffer, who was working on a campaign calling for the release of jailed women’s rights activists in Saudi Arabia, received an anonymous message in Arabic in the WhatsApp smartphone application. The message was found to contain a link that would install the malware program Pegasus—developed by an Israeli cyberintelligence firm—which allows a third party to spy extensively on an encrypted phone’s calls, photos and messages. Amnesty warns the attack was likely part of a much broader effort to spy on activists in several countries across Asia, Africa and Europe.