Experts in mobile phone security said TikTok concealed the tactic in "unusual added layer of encryption" that violates Google's policies limiting how apps track people. It also was not disclosed to TikTok users.
Tests show that TikTok ended the practice in November.
"The White House has said it is worried that users’ data could be obtained by the Chinese
government and used to build detailed dossiers on individuals for blackmail or espionage," according to the WSJ.
TikTok says it is “committed to protecting the privacy and safety of the TikTok community."
"Like our peers, we constantly update our app to keep up with evolving security challenges," a company spokesperson told the WSJ, adding that the the "current version of TikTok does not collect MAC addresses.”