The alleged money man died in a pile of burnt cash. He was riding in a car in Gaza City when the Israeli missile struck. The blast tore apart the vehicle, ripping open bags of American dollars and blowing the bills across the street. An unidentified witness told the New York Times that security soon collected the dollars billowing across the road and searched the car for more.

The man behind the bills, Israel says, was a high-level Hamas official named Muhammad al-Ghoul. He allegedly managed the group’s finances — its “terror funds,” as Israel said — and his death this week represents the latest in a series of Israeli strikes targeting the militant faction’s ranking commanders. Late last week, Israel killed three top Hamas leaders in what Prime Minister Benjamin Netanyahu characterized as a result of “extraordinary intelligence,” a boast of necessity for him after Israel’s failure to detect the many tunnels Hamas had built between Gaza and Israel over the past year.

Israeli analysts, in interviews with Washington Post reporters, also framed the strikes as a triumph of intelligence. One said it signaled “a leak in the system somewhere, a system that until now was tight and compartmentalized.” Another added: “Our firepower, our intelligence and our capability to sustain are bigger than” Hamas’s.

While it’s not entirely clear how the Israel military ferreted out the locations of the militant leaders, Hamas quickly concluded that Israeli spies — or “collaborators” — were to blame. Late last week, Hamas executed at least 18 Palestinians suspected of collaborating. Their purported confessions, according to Al-Monitor, involved “delivering information on resistance members who have been targeted, providing detailed descriptions of the houses of a number of resistance members that have been destroyed during the war.” The Gaza Ministry of Interior explained further that the executed were “spies” who had funneled to Israel “important information about the resistance, which led to the assassination of some figures.”

If true, that may be reassuring to some Israeli security experts, who have worried publicly in recent years that Israel was over-dependent on technology in intelligence gathering at the expense of human resources.

“The intelligence agencies need to stop and reexamine their quest for the magical solutions of cyber tools,” wrote Gabi Sidoni, of Israel’s Institute for National Security Studies, in a Haaretz opinion piece in July. “The accomplishments in the war on suicide terror a decade ago were the result of a balance between technology and the human element – a balance that has been broken in recent years.”

“There is no substitute to a human source, because a human source goes into their house, sometimes even into their minds,” Yaakov Peri, a former official with Shin Bet, the Israeli domestic intelligence service, told the New York Times. “With all the technology — drones, you name it — you need a background, and you need the assistance from a human source.”

Judging from Hamas swift retributions, notwithstanding the intelligence failure on the tunnels, those human sources are plentiful, whether blackmailed, cajoled or coerced into service. To Hamas, they’re traitors of the worst order, and are to be executed — as when masked gunmen shot dead six suspected collaborators in 2012, dragging one of them through the streets behind a motorcycle while residents screamed, “Spy! Spy!”

During the First Intifada in 1987 and 1994, it’s believed as many as 1,000 suspected collaborators were killed by other Palestinians. “In Palestinian society, to call someone a collaborator is to call him a traitor,” wrote expert Hillel Cohen, who has authored two books on collaborators, in his book “Army of Shadows.”

When Hamas swept into power in 2007, it made clamping down on collaborators a top priority, Al-Monitor reports. “Nobody knows how many pro-Israel intelligence agents operate in the Palestinian territories,” Al-Monitor’s Adnan Abu Amer wrote in 2013. “No official statistics from Palestine or Israel have been issued, nor have any exact numbers been provided.” Some estimates say there could be fewer than 10,000 “undercover agents.”

“The inhabitants of the Gaza Strip exchange whisper stories of spies and mistrust any stranger who asks the wrong question or encounters resistance fighters or their families at the wrong time,” writes Palestinian journalist Asmaa Al-Ghoul.

And today, this clandestine force of spies and “undercover agents” appear to be one of the strongest weapons at Israel’s disposal. “Hamas is in a panic that their organization has been penetrated by Israeli intelligence,” one former Israeli security official told the Post. “And they are trying to find who is helping Israel to target their leaders.”