A request by President Trump’s voter fraud commission for data from states could pose a threat to national security, according to former Homeland Security Secretary Michael Chertoff.

Michael Chertoff, who led DHS under President George W. Bush from 2005 to 2009, wrote in an op-ed for the Washington Post on Wednesday that if “sensitive data is to be collected and aggregated by the federal government,” the Trump administration must ensure the information is not targeted by hackers.