Pulling the Plug on TikTok Will Be Harder Than It Looks

“A lot of this is a game of chicken,” said James A. Lewis, who runs the cyberthreats program at the Center for Strategic and International Studies. But he believes Mr. Biden has a far greater chance of success than his predecessor did.

“Different from the Trump administration, I think this administration has a chance of winning — attitudes have changed toward China,” he said. Several new bills that would, in different ways, give explicit new authority to the president to shut down TikTok have received bipartisan support. They are propelled by the intelligence community’s conclusion, contained in the Worldwide Threat Assessment delivered to Congress, that China remains the “broadest, most active and persistent” cyberthreat to the country.

Yet so far, the threat from TikTok is largely theoretical.

There have been a handful of cases of abuse, including efforts to geolocate reporters who published leaked information about the company. But the administration has not presented comprehensive, declassified evidence of a systemic effort to use the app to advance the Chinese government’s collection efforts.

That has not stopped nearly 30 states from banning TikTok from official government or contractor phones, and federal employees are being made to remove it as well — though not from their personal devices.

There are three areas of clear concern. The first is where TikTok stores the data of its United States users. Until recently, much of it was on ByteDance-run servers in Singapore and Virginia, which many feared would allow China to require TikTok to turn over user data under Beijing’s national security laws. This year TikTok tried to pre-empt this argument, saying it would delete the data of its American users from the ByteDance servers and move them to servers run by Oracle, an American cloud computing firm.

Then comes the harder question — who writes the algorithm, the code that is TikTok’s secret sauce. That code assesses a user’s choices and uses them to select more material to feed the user — a favorite dance routine, or maybe an interesting news story. The algorithms have been written in China, by Chinese engineers who have refined the art of giving users what they want to see. The worry, Matt Perault and Samm Sacks wrote recently on the Lawfare blog, is that “TikTok could unilaterally decide to prioritize content that would threaten or destabilize the United States.” Again, it hasn’t happened yet, at least not through TikTok.

And finally, there is the issue of whether an app whose algorithm few understand could be a gateway for outsiders, including the Chinese ministry of state security, to get into the phones of Americans — to find out not their dance preferences, but the vast trove of data they carry around in their hip pockets.