HONG KONG — The police officers who came to take away Owen Chow on national security grounds last week left little to chance.

Determined to find his phones, they had prepared a list of cellphone numbers registered to his name, even one he used exclusively for banking, the 23-year-old Hong Kong activist said. Officers called each number in succession, the vibrations revealing the locations of three iPhones around his apartment.

By the end of their raids, police had amassed more than 200 devices from Chow and 52 others held that day for alleged political crimes, according to those arrested, as well as laptops from spouses who are not politically active and were not detained.

The digital sweep showed how Hong Kong authorities are wielding their new powers under the national security law — introduced last summer — far more widely than the city’s leader promised. Since the Jan. 6 raids, authorities have blocked at least one website, according to the site’s owner and local media reports, raising concerns that Hong Kong is headed for broader digital surveillance and censorship akin to that in mainland China.

“It is a redo of the Great Firewall,” said Lokman Tsui, an assistant professor at the Chinese University of Hong Kong who specializes in privacy and online communications. “They are testing the waters for now, so the results are uneven — but it is a question of when and how, not if.”

Hong Kong police have begun sending devices seized from arrested people to mainland China, where authorities with sophisticated data-extraction technology are using the information from those devices to assist in investigations, according to two people familiar with the arrangement who spoke on the condition of anonymity to protect their safety.

Glacier Kwong, founder of Keyboard Frontline, which tracks digital rights in Hong Kong, said the government clearly intends to crack down on one of the last free spaces for dissent.

“The government has actually set a precedent,” Kwong said. “As long as it is not to the liking of the regime, a website can be blocked without any reason under the national security law, which is a clear blow to the freedom of the Internet, freedom of information and freedom of speech.”

In emailed comments to The Washington Post, a Hong Kong police spokesman said the force would not comment on specific cases but pointed out that the national security law allows police to unilaterally disable access to online content. Police would not disclose details of investigations, he added.

A day after The Post published this report, police spokesman Kwok Ka-chuen denied that seized devices were sent to mainland China.

Data sweep

The dozens arrested last Wednesday spanned the pro-democracy spectrum, from civil society activists — labor unionists and promoters of rights for minorities and the disabled — to former lawmakers. Two already in custody, former student protest leader Joshua Wong and radio presenter Tam Tak-chi, were rearrested.

Their alleged crime was participating in a primary vote to choose candidates who would later run in legislative elections that the pro-democracy camp stood a strong chance of winning. (Only half of Hong Kong’s legislature is directly elected, a feature designed to maintain the pro-
Beijing establishment’s hold on power.) The city’s government subsequently postponed the elections, citing the coronavirus pandemic.

All but the two already in detention and the former Democratic Party chairman Wu Chi-wai were released on bail, and none have been charged under the security law. If charged and convicted under that measure, they could face life in prison.

Police have been seizing devices from protesters arrested at ­anti-government rallies since late 2019, but the targeted roundup under the national security law ensnared almost every prominent opposition figure.

Shortly after the arrests and device seizures, colleagues and associates of those detained started noticing strange activity on their social media and email accounts. Tam, already in jail, appeared to join the encrypted messaging app Telegram, popular with Hong Kong protesters, and to be contacting people through it. The administrator of his Facebook page said Tam had not reactivated his Telegram account, and urged people to ignore the messages.

Ray Chan, a former pro-democracy lawmaker arrested at his home, said he kept receiving confirmation codes sent by Telegram to a replacement phone after police confiscated his devices. The codes are used to verify the authenticity of a user trying to log into an account.

Separately, Lam Cheuk-ting and Helena Wong, two former Democratic Party lawmakers, said their staffs received notifications from Google that state-sponsored hackers were trying to breach their work accounts, which are hosted on a Gmail server. The Google alerts arrived just after their arrests, once their devices were in the hands of police.

“They are spreading the net and are using all means to collect information,” Lam said in an interview. “If there is any information they find that they can use to charge us, they will continue to dig.”

A Hong Kong police officer, speaking on the condition of anonymity to discuss sensitive details, said the force’s Cybersecurity and Technology Bureau is unable to crack newer Apple iPhone models locally but has found ways to compromise Android systems and information on Google Drive once police have seized a person’s devices.

A Google spokeswoman said she could not comment on specific incidents. Notifications of a government-backed hacking attempt are sent even when Google may have already successfully blocked the attempt.

One of the people familiar with police practices who spoke to The Post said that the force remains convinced that pro-democracy protests that gripped Hong Kong in 2019 were highly planned and coordinated, though they were largely leaderless. Police believe they need to fully map out pro-
democracy and civil society links in the city to have a clearer picture, this person said.

Activists fear the same.

“The government would like to map the network of the opposition with the devices they confiscated, like who is in contact with who, to completely crack down on us,” said Kwong, the digital rights activist, who lives in exile in Germany.

Access restricted

After the arrests, Hong Kong users reported trouble accessing HKChronicles, a website founded during the 2019 anti-government movement. The website is known for publishing personal details of Hong Kong police officers and pro-Beijing figures; it also identifies businesses in Hong Kong that support the Chinese government, allowing protesters to boycott them.

In a post on the HKChronicles Telegram channel last week, ­Naomi Chan, the website’s owner and chief editor, said she noticed that site visitors had “decreased drastically.” Users trying to reach the site from different Internet service providers based in Hong Kong received error messages.

HKChronicles has since changed IP addresses, Chan said on the Telegram channel. The site continues to be inaccessible locally except via a virtual private network.

Four of the major Internet service providers in Hong Kong did not respond to requests for comment or declined to comment. Chan, an 18-year-old high school student, did not respond to messages sent via Telegram.

Businesses and technology companies have been bracing for fallout from the national security law and are sensitive to any moves that undermine the unrestricted nature of the Internet in Hong Kong — something that has distinguished the city from the Chinese mainland. Google, Facebook and other U.S. social media companies are blocked in China, but operate freely in Hong Kong.

Experts say that technical attempts to block online content, so far, are clumsy and less sophisticated than methods used in mainland China. They predict a lighter touch than China’s Great Firewall so as not to drive away businesses in the financial center.

But none doubt that this is the beginning of unprecedented restrictions on the Internet in Hong Kong. “The Internet is really the only place that we can breathe a little, so it is not surprising to me that they are trying to colonize that space now and invade it, too,” said Tsui, the CUHK professor.

This report has been updated to include an additional response provided by the Hong Kong police after publication.

Theodora Yu contributed to this report.