China has allegedly had the details of one billion residents leaked, in what could be the biggest personal data hack ever.

Unknown hackers claim to have obtained nearly 24 terabytes of data from a Shanghai police database, claiming it contains information on one billion people and “several billion case records”. The data leaked is said to be of all ages, including children’s personal information. The data include names, addresses, birthplace, national ID numbers, phone numbers, and crime and case details. The hackers offered to sell the data for around $200,000 (~£160,000) worth of Bitcoin on an online hacking forum.

The scale of the alleged leak has shocked the Chinese security community, triggering speculation about the credibility of the claim and how it could have taken place. Zhao Changpeng, founder and Chief Executive Officer of cryptocurrency exchange Binance, tweeted on Monday the company had detected the breach of a billion resident records “from one Asian country,” and had since increased verification procedures for potentially affected users.

Shanghai authorities have not publicly responded to the alleged hack. Domestic breaches are rarely disclosed because of a lack of transparent reporting mechanisms. In 2016, personal information on dozens of Communist Party officials and industry figures from Jack Ma to Wang Jianlin was said to have been exposed on Twitter – one of the country’s biggest online leaks of sensitive information at the time. This latest incident again highlights the challenges facing Beijing as it collects data on hundreds of millions of people while tightening national policing of online content.