LONDON: Israel’s military surveillance agency, Unit 8200, has used Microsoft Azure cloud services to store recordings of millions of mobile phone calls made daily by Palestinians in Gaza and the West Bank since 2022.

The cloud-based storage platform has enabled the execution of lethal Israeli airstrikes and has influenced military operations in Gaza and the West Bank, according to a joint investigation by The Guardian, the Israeli-Palestinian publication +972 Magazine and the Hebrew-language outlet Local Call.

After a meeting in late 2021 between Yossi Sariel, the head of Unit 8200, and Satya Nadella, Microsoft’s chief executive, work commenced on a customized, segregated area within the Microsoft Azure cloud platform for the Israeli intelligence agency to store a vast archive of daily communications from Palestinians.

Unit 8200, the rough equivalent of the US’ National Security Agency, had determined that the Israeli military’s servers lacked the necessary storage space and computing power to handle the volume of phone calls from an entire population — about 3 million Palestinians in the West Bank and another 2.3 million in Gaza.

Sources revealed that the “a million calls an hour” mantra that spread within Unit 8200 captured the project’s scale, using Azure’s near-limitless storage capacity to collect and store recordings of millions of Palestinians.

The new system allowed intelligence officers to store and replay the content of cellular calls made by Palestinians, uncovering conversations from a wider pool of ordinary civilians. Sources described the system as indiscriminate and intrusive, labeling it as a tool that turned an entire population into an “enemy.”

Israel controls the telecommunications networks in both the West Bank and the Gaza Strip. However, the latter has been severely damaged by Israel’s military campaign that began in late 2023, which has resulted in the killing of more than 60,000 Palestinians, including 18,000 children.

In Gaza, intelligence from phone call data in Azure was reportedly used by Unit 8200 to identify bombing targets. Officers would analyze calls from Palestinian individuals nearby when planning airstrikes in densely populated areas with many civilians, sources said.

Microsoft is under pressure from both employees and investors regarding its links to Israel’s military and the role its technology plays in Gaza. In May, an employee interrupted a keynote speech by Nadella, shouting: “How about you show how Israeli war crimes are powered by Azure?”

In 2022, the system initially focused on the West Bank, which is under Israeli military occupation. Sources from Unit 8200 said that the information stored in Azure served as a rich intelligence source, and that the Israeli military used it to blackmail individuals, detain them or justify killings afterward.

“When they need to arrest someone and there isn’t a good enough reason to do so, that’s where they find the excuse,” one said, referring to the information stored in the Microsoft cloud.

By July this year, about 11,500 terabytes of Israeli military data, roughly 200 million hours of audio, was stored on Microsoft’s Azure servers in the Netherlands, with some in Ireland. It is unclear if all the data is from Unit 8200 or other Israeli military units, sources said.

During the development of the system, Microsoft and Unit 8200 engineers collaborated to implement advanced security measures in Azure, in order to meet the Israeli unit’s standards. The project was highly secretive, with Microsoft staff instructed not to mention Unit 8200, which informed Microsoft that it planned to gradually migrate up to 70 percent of its data to the cloud, including both secret and top-secret information.

“The rhythm of interaction with (the unit) is daily, top down and bottom up,” one leaked document said.

Microsoft responded to the report, saying: “At no time during this engagement ... has Microsoft been aware of the surveillance of civilians or collection of their cellphone conversations using Microsoft’s services, including through the external review it commissioned.”

It added that its “engagement with Unit 8200 has been based on strengthening cybersecurity and protecting Israel from nation state and terrorist cyberattacks”.

Sariel resigned late last year after leading Unit 8200 since early 2021. He is described as a tech evangelist who adopted a vision of military and intelligence agencies migrating to the cloud.

He reportedly accepted responsibility for Unit 8200’s role in the intelligence and operational failure that led to the Hamas-led attack on Israel on Oct. 7, 2023, which resulted in the deaths of 1,200 people and the abduction of almost 240 others.

He declined to comment on the report. An Israeli military spokesperson told The Guardian that its work with Microsoft was based on “legally supervised agreements.”

It added: “The IDF operates in accordance with international law, with the aim of countering terrorism and ensuring the security of the state and its citizens.”