California Democratic Congressman Ted Lieu on Friday asked the House Oversight Committee to launch an investigation into President Donald Trump’s use of an insecure Android smartphone. Trump’s well-documented attachment to the device is, Lieu says, a threat to national security.

“Cybersecurity experts universally agree that an ordinary Android smartphone, which the President is reportedly using despite repeated warnings from the Secret Service, can be easily hacked,” reads Lieu’s letter in part.

That inherent risk is why the President is issued a specially-designed secure cell phone. But that phone reportedly lacks many basic functions. That almost certainly includes President Trump’s favorite mobile app, Twitter.

Trump was open about his resistance to ditching his preferred device, by some accounts a highly vulnerable Samsung Galaxy S3. Reports since the inauguration have had Trump giving up the phone—or, then again, maybe not.

By most accounts Trump does not use email, reducing the likelihood of sensitive or classified information being leaked through a hack of the phone. But it could be used for eavesdropping, to track the President’s location, or to spread malware to other devices in the administration.

But most novel—and chilling—security threat comes from the President’s reliance on Twitter to communicate with the public. The President’s often strongly-worded pronouncements have the proven ability to trigger stock moves, and his frequent baiting of foreign leaders has been described as “diplomacy by tweet.”

Trump’s Twitter account falling into the wrong hands, then, could have swift, possibly serious consequences for the global economy and worldwide diplomacy. A malicious actor with the creativity to antagonize the world more effectively than Trump himself could wreak plenty of havoc in just a few minutes.

According to Congressman Lieu, the President’s apparent indifference to that possibility amounts to an “egregious affront to national security.”

This story originally appeared on Fortune.com. Copyright 2017