A U.S. senator, Tom Cotton, has sought clarification from the Department of Defense on Microsoft’s alleged use of Chinese engineers for the maintenance of military cloud computing systems, according to a recently revealed letter.

The senator, a Republican representing Arkansas and serving as the chair of the Senate intelligence committee as well as a member of the armed services committee, addressed his letter to Defense Secretary Pete Hegseth. This letter was prompted by a report published by investigative journalism publication ProPublica earlier this week.

The report alleged that Microsoft had employed Chinese engineers to work on U.S. military computing systems, supervised by U.S. ‘digital escorts’. These escorts, hired via subcontractors, had the necessary security clearances but often lacked the technical acumen to assess if the Chinese engineers’ work could potentially pose a cybersecurity threat.

Microsoft, a major contractor for the U.S. government whose systems have previously been breached by Chinese and Russian hackers, declined to comment on the allegations. However, the company did inform ProPublica that its practices were disclosed to the U.S. government during an authorization process. The Defense Department, at this time, has not issued any response.

Senator Cotton has requested from the Department of Defense a detailed list of all contractors utilizing Chinese personnel, as well as additional information on the training provided to U.S. ‘digital escorts’ to detect suspicious activity.

In his letter, Cotton stated, “The U.S. government recognizes that China’s cyber capabilities pose one of the most aggressive and dangerous threats to the United States, as evidenced by infiltration of our critical infrastructure, telecommunications networks, and supply chains,” further emphasizing the importance to “guard against all potential threats within its supply chain, including those from subcontractors.”

This raises important questions about the security of U.S. military technology and the role of foreign personnel in its development and maintenance.