The US Department of Homeland Security (DHS) has banned the use of DeepSeek by civilian federal agencies, citing security concerns.

The ban covers any technology built with the aid of the company's AI models, and applies to agencies including the Department of the Treasury, the Department of State, and the Department of Justice, as well as prime contractors and subcontractors serving federal agencies.

It also bars DeepSeek from future procurements, and requires agencies to remove versions put into place prior to the ban.

The main worry is that DeepSeek servers are located in the PRC, where government cyber and intelligence operations legally have broad authority to access private company infrastructure.

"For DeepSeek-hosted instances of their models, DeepSeek's account generation process collects personally identifiable information (PII) and may also track and digitally fingerprint users. DeepSeek's most widely used applications function through a prompt-and-response process that requires presenting information to the model, and which may result in the transfer of sensitive data to the PRC if used by US government employees or vendors," the notice reads.

"The transfer of the aforementioned information to the PRC, either independently or in combination with publicly available data could produce actionable intelligence on US persons and/or government programs."

DHS cites DeepSeek vulnerability concerns

The DHS is also concerned that the models themselves may contain malware or other security vulnerabilities. Indeed, open source security research has already found that the DeepSeek iOS mobile application contains multiple critical vulnerabilities.

Agencies that have been using DeepSeek are warned that they should check that they haven't already been compromised. According to the DHS, these organizations should monitor the flow of traffic in and out of the agency, implement enhanced logging and controls for relevant systems, and flag any anomalous activity.

Gabrielle Hempel, security operations strategist at Exabeam, said the advisory “raises some significant questions” with regard to supply chain security.

"What I find particularly interesting about the DeepSeek order is the breadth of its language," Hempel commented.

"The restriction extends beyond DeepSeek itself to third-party products and services developed using its implementations, which raises some significant questions about software provenance and supply-chain compliance."

DeepSeek is already banned from state systems in Texas, New York, and Virginia, as well as in Australia, South Korea, and Taiwan. Individual US government bodies, including the Commerce Department and the US Navy, have also removed it from use.

It remains to be seen how effective such bans can be, however, and how quickly existing systems based on DeepSeek can be replaced or redesigned.

"I suspect we're going to see increasing tension between national security policy and the practical realities of AI development, particularly as governments begin imposing restrictions that extend beyond the models themselves and into the broader software supply chain," said Hempel.

"The challenge will be making those requirements sufficiently clear and technically enforceable.”

The ban comes just days after the release of DeepSeek's latest AI model, V4.1-Flash-1017, which the company described as faster and more efficient than previous models.

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