What's the use of those fraud groups to defraud users of personal information?

Personal information can be resold to the third party in need, and the third party can use this information to recommend their products or services to you. You can also directly use your information for illegal activities.

Personal information is very harmful after being leaked, such as:

Spam messages keep coming, harassing phone calls come one after another, spam messages are overwhelming, fake cards are overdrawn, cases and accidents fall from the sky, criminals come to cheat, pretend to be public security personnel to ask for money transfer, cheat and steal, account money is missing, and personal reputation is damaged for no reason.

Extended data

According to the relevant provisions of China's criminal law:

Article 253-1 Staff of state organs and financial, telecommunications, transportation, education, medical and other units. Whoever, in violation of state regulations, sells or illegally provides personal information of citizens obtained by the unit in the course of performing its duties or providing services to others, if the circumstances are serious, shall be sentenced to fixed-term imprisonment of not more than three years or criminal detention and shall also or only be fined.

Whoever steals or illegally obtains the above information by other means, if the circumstances are serious, shall be punished in accordance with the provisions of the preceding paragraph.

Where a unit commits the crimes mentioned in the preceding two paragraphs, it shall be fined, and the persons who are directly in charge and other persons who are directly responsible shall be punished in accordance with the provisions of each paragraph.

References:

Baidu Encyclopedia-Personal Information Disclosure

References:

Baidu encyclopedia-privacy right