It looks like one of the most controversial policies of US border security is now being adopted by China: Searching through smartphones. Reports say Chinese border agents are requesting to check the phones of some Hongkongers suspected of joining anti-government protests.

Some of the city’s residents, both local and foreign, have been asked to hand in their phones for inspection when crossing the border into mainland China, according to the South China Morning Post

The main target appears to be pictures of anti-government protests, but some travellers revealed that immigration officers have also gone through private messages.

“They asked if I supported the protesters and kept saying that Hongkongers were bribed and manipulated by foreign forces,” one of the travellers told the Post, claiming he was kept at the border for six hours.

One consultant told reporters that he was not allowed to go back to Hong Kong after he refused to let Chinese customs officers check his smartphone. (Picture: Handout)

The border between China and Hong Kong is a busy one, with thousands of commuters travelling to work in both directions each day. On Hong Kong’s Reddit-like forum LIHKG, popular among protesters, people have been discussing how to protect their privacy. The most common warning is deleting any photos connecting them to the protests.

However, experts have warned that this might not be enough.

According to independent security researcher Jane Manchun Wong, a good place to start is switching from biometric locks like fingerprint and FaceID to more old-school PIN codes and passwords.

Another tip is to reduce the amount of personal information on the phones by uninstalling or logging out of certain apps. Users can also add two-factor authentication for online accounts that might be more sensitive.

“One thing to note is that, once the authority has unlocked your phone and used it, you should assume the data and security on your phone has been compromised,” said Wong. “Backdoors might be installed without users being aware of it.”

Chinese human rights lawyer Chang Boyang told SCMP it was unlawful for immigration officers to examine the contents of travellers’ mobile phones. (Picture: Handout)

Smartphone checks are not unique to China. US Customs and Border Protection has also become notorious for the practice following a surge in smartphone checks at airports in recent years. 

However, Chinese border security has been known to take things even further. A joint media investigation in July found border officers were installing spy apps on foreign travellers’ phones at the Kyrgyzstan-Xinjiang border. 

The forensics app reportedly cross-checks files on smartphones with a list of 73,000 items considered sensitive, many of which are related to Islam. This crossing in particular is sensitive because Xinjiang is home to the Uygur Muslim minority, a group subject to heavy monitoring and believed to be subjected to mass detention and human rights abuses.

One possible fix for this is reinstalling the smartphone’s operating system, Wong said, but it’s not guaranteed to remove all possible backdoors. Instead, travellers may want to consider getting a second phone.

Glacier Kwong agrees. As a core member of freedom advocacy group Keyboard Frontline, Kwong has even stricter precautions for those joining the protests, most of which are already donning face masks to hide their identities and resorting to encrypted messaging apps like Telegram to organize the tech-fueled protests.

“If people really do have to go back to China, then they must not bring a phone they usually use,“ she said. “I would suggest that they bring a 'clean' phone for China particularly.”

Protesters in Hong Kong have been hiding their identities and refusing to name leaders to avoid legal repercussions. (Picture: Felix Wong/SCMP)

Kwong suggests another idea might be ditching Chinese apps since China's cybersecurity law says that companies operating in the mainland need to hand over user data if government security agencies require it.

Protesters seem to already be aware of the fact that their smartphones might contain valuable data that could be used against them. As tensions have escalated, app download charts in Hong Kong have been steadily filling with apps meant to keep data encrypted, locations hidden and smartphones locked from prying eyes. And soon, it seems, there might also be a spike in demand for burner phones.