Israel's Unit 8200 - its military surveillance agency - is storing vast amounts of intelligence data on Palestinians in the West Bank and Gaza on Microsoft Azure.

Unearthed through an investigation conducted by The Guardian, Israeli-Palestinian publication +972 Magazine, and Hebrew publication Local Call, the cloud platform is hosting audio files from millions of phone calls made by Palestinians.

According to The Guardian, the agreement was made in 2021 between Satya Nadella and Yossi Sariel, who was the commander of Unit 8200 between 2021 and 2024. It then went live in 2022, giving the agency access to a customized and segregated area of Microsoft Azure, which is reportedly used for a mass surveillance tool.

Microsoft has previously confirmed it provided Israel's military with cloud computing services, though following an internal review said it had found "no evidence to date that Microsoft’s Azure and AI technologies have been used to target or harm people in the conflict in Gaza," while the Guardian report adds that Microsoft claims Nadella was unaware what Unit 8200 intended to use the services for.

At the time of the meeting, The Guardian reports that internal recordings of the conversation between Nadella and Sariel did not include explicit statements of Unit 8200's plan, instead referring to "sensitive workloads" of secret data.

However, the recent investigation has found several documents detailing how Unit 8200 was using Azure - stating that it would include raw intelligence and audio files, while interviews with 11 sources from Microsoft suggest that some knew what the project hoped to achieve.

Three sources from Unit 8200 have also said that Microsoft Azure had facilitated the preparation of deadly airstrikes - including the identification of bombing targets - and "shaped" military operations in Gaza and the West Bank.

Use of the system also increased during the campaign in Gaza, which killed more than 60,000 people, including more than 18,000 children. In the West Bank, Unit 8200 sources said that data stored in Azure had been used to blackmail people, place them in detention, or justify killing after the fact.

The surveillance system used by Unit 8200 has given it the ability to access and play back phone calls made by Palestinians even outside of the occupied territories, bringing ordinary civilians into the mix. The sources told The Guardian that Unit 8200's leadership turned to Microsoft after realizing it had insufficient storage space or computing power.

Microsoft engineers reportedly developed enhanced layers of security for the servers to be used by Unit 8200, of which, according to the files accessed by The Guardian, around 11,500 terabytes are hosted in Microsoft data centers in the Netherlands, and a smaller proportion in Ireland. Some of this may belong to other Israeli military units.

A Microsoft spokesperson told The Guardian that it did not have information about data stored by Unit 8200, and that conversations between the company and the agency had "been based on strengthening cybersecurity and protecting Israel from nation-state and terrorist cyber-attacks.”

The spokesperson added: “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.”

Unit 8200's Sariel declined to comment, but the IDF provided the following statement: “We appreciate Microsoft’s support to protect our cybersecurity. We confirm that Microsoft is not and has not been working with the IDF on the storage or processing of data.”

Microsoft has been seeing ramping criticism of its partnership with Israel's military. Employees of the company have staged protests, and on July 1, more than 60 shareholders signed a letter calling for the company to publish a report "assessing the effectiveness of its human rights due diligence processes" as a result of Microsoft's role in the Israel-Palestine conflict.

The lead filer, the Religious of the Sacred Heart of Mary, said: “From our founding in 1849, the Religious of the Sacred Heart of Mary, an international congregation of Catholic women religious, have been committed to our mission ‘that all may have life.’ As shareholders, we are deeply disturbed by Microsoft’s apparent ineffective due diligence with regard to human rights violations by its customers against the Palestinian people and others.”

The company did not address these concerns during its recent earnings call.