A few seconds of voice may be enough to clone
IT Home reported on October 11 that China's Ministry of State Security says a caller may stay silent after the line connects, to induce the other person to speak. A few seconds of that speech may then be used for AI voiceprint cloning and for impersonation fraud or other crimes.
The social-media line "stay silent for three seconds on an unknown call" refers to this warning. The silence is a way to give away less voice. It is not a set of instructions.
[1]
The warning is not only about voice
The ministry also says that voiceprints, faces, irises, and gait are hard to change and are being treated as data that can be collected and copied. The report lists over-collection and deepfakes as abuses already in use, and says deepfakes are used to fake an acquaintance asking for money and to spread rumors online.
This article does not describe how to pull features out of public material, or how to match gait or genetic data to a person.
[1]A line the court has already drawn
IT Home cites the Supreme People's Court: illegally obtaining, selling, or providing a citizen's face photos, videos, or other personal information, when the circumstances are serious, is the crime of infringing on citizens' personal information.
The report's rule is not to provide this information unless it is necessary, and to look first at the purpose, the scope, and the protections. It does not give a count of completed cases.
[1]