More than a half-dozen technology experts and former national security officials filed an amicus brief Tuesday urging a federal court to halt the collection of voter information for a planned government database.

Former national intelligence director James R. Clapper Jr., one of the co-signatories of the brief, warned that a White House plan to create a centralized database containing sensitive information on millions of American voters will become an attractive target for nation states and criminal hackers. This summer, the Presidential Advisory Commission on Election Integrity issued a sweeping request to state officials to submit voter data to "analyze vulnerabilities and issues related to voter registration and voting.” The commission, which is chaired by Vice President Pence and Kansas Secretary of State Kris Kobach (R), was established after President Trump claimed that he would have won the popular vote if not for as many as 5 million illegally cast ballots. State officials haven't found any indication that there was widespread voter fraud.

State officials and civil rights advocates have questioned the commission's stated mission and broad data collection, arguing that it could restrict voting.

But the brief focuses on the security implications of aggregating and housing sensitive information, such as names, addresses, party affiliation and partial social security numbers, in one central location, without adequate security and privacy safeguards. “A large database aggregating [personally identifiable information] of millions of American voters in one place, as the Commission has compiled and continues to compile, would constitute a treasure trove for malicious actors,” the signatories wrote.

The brief states that the commission does not appear to have established rules or procedures defining who gets access to the database or how it should be actively protected.

Armed with detailed voter information, foreign adversaries could conduct targeted information campaigns against specific groups of voters, echoing Russian interference during the 2016 election, the filing claims. Clapper and his co-signatories also said that the database will be situated on a re-purposed White House system, and not within the Department of Defense, making the information even more vulnerable to theft. “Aggregating a comprehensive and official set of such data onto one high-profile, widely publicized server maintained by the White House may reduce the technical and practical barriers to a foreign adversary acquiring such information and making use of it without detection,” the brief said.

Clapper and the other experts added that malicious actors could also alter the database itself, leading the Trump administration to act on false information. Such manipulation could eventually result in the wrongful removal of legitimate voters from voter rolls.

“We now know better than 12 months ago just how much foreign governments would like information on American voters,” said Joshua Geltzer, executive director of Georgetown’s Institute for Constitutional Advocacy and Protection and one of the co-authors of the brief.

A White House spokeswoman did not respond to a request for comment.

Filed in the United States District Court for the District of Columbia, the brief supports a lawsuit by Common Cause, a nonprofit government watchdog group, that seeks to halt the commission's collection of a wide array of sensitive data about American voters. Other signatories include the former director of the National Counterterrorism Center Matt Olsen, and former U.S. deputy chief technology officer Alex Macgillivray.