Hong Kong’s privacy watchdog has made its first arrest under a new law criminalising doxxing, detaining a 31-year-old man in West Kowloon.

The Chinese national was arrested on Monday after the Office of the Privacy Commissioner for Personal Data received a report by the alleged victim accusing the suspect of posting their personal details to an online platform, said Lo Dik-fan, of the watchdog’s criminal investigation division.

“This is the first action we have taken since doxxing was criminalised,” said Lo, who serves as acting senior personal data officer. “The case is related to a monetary dispute between the suspect and the victim.”

Authorities also confiscated a mobile phone in connection to the case.

Legal amendments making the malicious disclosure of personal information illegal took effect in October after being approved by the city’s legislature the month before. Under the new laws, the privacy commissioner can carry out criminal investigations and initiate prosecutions for doxxing.

In the first of the law’s two tiers, the unauthorised disclosure of a victim’s personal data – either with the intent to cause them “specified harm”, or with reckless disregard for the possibility of harm – is punishable by up to two years in jail and a fine of HK$100,000 (US$12,820).

Under the second tier, reserved for cases where such harm actually comes to pass, those penalties increase to a maximum of five years in jail and a HK$1 million fine.

Monday’s suspect was arrested under the offence’s first tier.

The legal amendments also empowered the privacy watchdog to order internet service providers to take down offending content, regardless of whether the disclosure was made in Hong Kong or overseas.

Anyone defying such a request without reasonable justification can be jailed for up to two years and fined as much as HK$50,000 for a first offence. They are also liable to an additional fine of HK$1,000 a day until the material is removed.

As Monday’s case was still under investigation, authorities declined to reveal which online platform was involved or whether any takedown order had been issued.

Lo also declined to say whether the offending content was still online, but nonetheless warned residents against spreading it in the event they had received it.

“If residents see any such information online, I strongly suggest they do not try and share it, as they could be breaking the law as well,” Lo said.

Before the law was amended to specifically criminalise doxxing, the privacy commissioner had been responsible for referring suspected cases to police, who pursued them as various other offences.

The watchdog said it had referred more than 1,400 cases to the police in the wake of the 2019 anti-government protests, which saw many officials, police officers, journalists and protesters’ personal information maliciously circulated on social media.

A total of 17 people were subsequently arrested, two of whom have since been convicted.

The first was a part-time waitress who managed a doxxing chat room, and who was jailed for three years on charges of conspiracy to incite others to commit arson and conspiracy to do any act with a seditious intention.

The second case involved an Immigration Department clerical assistant who was jailed for nearly four years for misconduct in public office after she used her position to dox 215 individuals.

The legal amendments outlawing doxxing, said to be some of the toughest in the world, were widely seen as a move by the government to curb the increasingly widespread behaviour in the aftermath of the 2019 protests.

By last year, doxxing complaints had fallen 76 per cent, the privacy watchdog has said.

Critics of the law have said its reach is too wide, and the Asia Internet Coalition, which represents firms such as Google, Facebook, Twitter and LinkedIn, previously warned the broad wording of the amendment was a potential barrier to trade and would discourage the companies from investing or offering their services in Hong Kong.