The non-profit Frontline Defenders disclosed its findings on Monday in a joint technical report together with Amnesty International and the University of Toronto’s Citizen Lab, which independently confirmed the results.
It is not clear who placed the NSO spyware, which surreptitiously gives intruders access to everything a person stores and does on their mobile phone, including real-time communications.
Three of the hacked Palestinians work for civil society groups. The others do not, and wish to remain anonymous, Frontline Defenders says.
Among those hacked is Ubai Aboudi, a 37-year-old economist and US citizen who runs the Bisan Center for Research and Development in Ramallah, in the occupied West Bank. The group is one of the six slapped with terrorist designations by Israel last month.
The Irish-based Frontline Defenders considers Israel the main suspect. The first two intrusions were identified shortly after Israeli Defence Minister Benny Gantz declared the six Palestinian civil society groups to be "terrorist" organisations.