https://techcrunch.com/2020/08/12/tiktok-found-to-have-tracked-android-users-mac-addresses-until-late-last-year/

Until late last year social video app TikTok was using an extra layer of encryption to conceal a tactic for tracking Android users via the MAC address of their device which skirted Google’s policies and did not allow users to opt out, The Wall Street Journal reports. Users were also not informed of this form of tracking, per its report.

Its analysis found that this concealed tracking ended in November as US scrutiny of the company dialled up, after at least 15 months during which TikTok had been gathering the fixed identifier without users’ knowledge.