When Chinese Premier Li Keqiang visited Australia in March, one social media platform lit up with an unusual question: “Will you go to welcome the Premier?” This discussion was not on Facebook or Twitter but on WeChat, China’s most popular messaging app, owned by the tech titan Tencent.

Unconfirmed rumours on ­WeChat pointed to the Chinese consulate-general in Sydney and the pro-China Australian Council for the Promotion of Peaceful ­Reunification of China as key backers of the well-organised campaign. Regardless of who was behind it, why was a rally in ­Australia being ­arranged on a ­Chinese social media platform?

WeChat is probably not on the radar of most Australians, two-thirds of whom use the US platform Facebook, but it has carved out a niche in Australia with some troubling implications, most ­notably the direct Chinese government censorship of Australian citizens within Australian borders.

Getting to the bottom of ­WeChat’s market penetration in Australia is not easy. The company does not publish statistics and, when contacted, the head office in China would not disclose them. However, several social media firms have sprung up in Australia offering to market products or messages to Australians using WeChat.

These agency partners of ­WeChat claim to be provided with the elusive market data. I spoke to three, who quoted average monthly active users in Australia of more than one million people. One quoted recent figures of 1.5 million.

Given users of WeChat predominantly communicate in Chinese, that seems an upper limit.

The Australian Bureau of Statistics reported 650,000 people who spoke Chinese languages at home in 2011 (a number that has almost certainly risen since and excludes those who speak ­Chinese but not at home).

The Department of Education reported 140,000 Chinese international students in its latest statistics and Tourism Australia records 1.2 million Chinese visitors in the year to April.

WeChat’s successful penetration of the Chinese-speaking Australian population raises ­several challenging issues.

The first is the unacceptable censorship regime the Chinese Communist Party is imposing on a large body of Australian nationals as well as visiting international students and tourists. China’s domestic censorship online and offline is notorious. Less often ­discussed is China’s ability to ­extend this censorship regime into ­Australia.

Research conducted by the Citizen Lab at the University of Toronto last year has documented the extensive but subtle censorship imposed on WeChat users by the Chinese authorities. That includes blocking messages that contain censored keywords (such as Tiananmen massacre or Radio Free Asia), links to banned websites (including gambling, pornography and news sites critical of the Chinese government) and images with banned political content (such as images associated with controversial events including human rights crackdowns).

The censorship can be hard for users to detect.

For example, when a user sends a message with a censored keyword, they are not advised their message was blocked; the message just doesn’t appear on the receiver’s end. The censorship regime is also far stricter in group chats than private messages, suggesting an effort by the authorities to prevent mass dissemination of messages potentially damaging to the Communist Party.

Through rigorous testing, the Citizen Lab was able to demonstrate that users who originally sign up with a mainland Chinese mobile number, then later switch to an international number, remain under the same censorship as they would back in China. This has the potential to sweep up Australian holidaymakers, migrants of Chinese descent (more than a half-million Australians were born in China), students, academics and business people.

While users who establish a new account from Australia can avoid keyword censorship on ­WeChat, they still have some websites blocked and are subject to any future changes imposed by the Communist Party as it continues to tighten censorship at home.

A second issue is how China may use WeChat’s success here to further interfere in Australian internal affairs. Researchers have observed the softening tone of Australia’s Chinese language media towards the Chinese ­government during the past decade or two. In part this has been ­explained by shifting generations of Chinese arrivals from the pre and post-Tiananmen eras. It also has involved an accompanying shift in ownership. Recent claims have it that up to 95 per cent of Australia’s Chinese language newspapers are controlled by ­Chinese state-owned companies.

Where China failed to successfully connect with the earlier wave of Chinese immigrants, it has been far more assiduous in targeting the post-Tiananmen generation. China experts Linda Jakobson and Bates Gill say in their recent book China Matters that “engagement and mobilisation of overseas ­Chinese are important elements in Beijing’s foreign policy strategy overall and in its soft power in ­particular”.

So how may the Communist Party harness WeChat’s success in Australia to pursue these ends? The 2008 Chinese Olympic torch relay, where thousands of Chinese students were bused to Canberra to counter protesters, showed the Chinese government was not shy about mobilising and funding Chinese-Australians to boost China’s status. As the example at the start of this article also suggests, similar mobilisations have been undertaken for other high-level Chinese visits. WeChat’s reach into a large proportion of Chinese-speaking Australia clearly represents an easy vehicle for future efforts, ­especially when they are primed by limiting their exposure to negative news stories about China.

There are also more sinister potential applications. As Jakobson and Gill write, “the Chinese embassy maintains a close watch for dissident behaviour, both among Chinese citizens in Australia — such as students — and Australians of Chinese descent. They do so through the cultivation of ­informants within the Chinese community who are willing to pass along information about the ­political, social and religious practices of other Chinese. This is ­relayed to intelligence authorities in China to assess and, if deemed necessary, act upon.”

WeChat offers a far more streamlined means of monitoring overseas citizens and Australians of Chinese descent.

WeChat highlights the new world of censorship silos we all face as a consequence of the rise of social media. Whereas the Australian government once determined domestic censorship standards, today it is increasingly foreign governments and companies that decide what Australians can and cannot see. The dominant platform in Australia, Facebook, while a private company with very ­different motivations and levels of responsiveness to WeChat, has its own censorship regime. In 2012 its bizarre rules for censoring content were leaked, famously exposing a ban on images of breastfeeding if nipples were exposed but allowing crushed heads and limbs as long as no insides were showing. Since then, in response to public criticism, Facebook has become far more transparent about what ­content it filters out.

While these social platforms cannot stop newspapers, bloggers and others from writing what they want, they are increasingly the platforms where we gather our news. So they can, and do, act as gatekeepers on content.

A 2016 Deloitte tracking survey found the proportion of Australians using social media as their primary source of news had ­doubled across 12 months to almost one in five. Increasingly, these platforms determine what we read and watch.

China routinely demands other countries refrain from interfering in its internal affairs. Australia should expect the same in return and insist on an end to Chinese Communist Party censorship of Australians. The government should also require that all social media companies publish their censorship rules as a condition of operating in Australia. While we wait, Australians are stuck suffering FOMO (fear of missing out).

Fergus Hanson is head of the International Cyber Policy Centre based at the Australian Strategic Policy Institute.