Chinese swimmer Sun Yang’s rivalry with Australia’s Mack Horton has spilled out of the pool at these Olympics, sparking angry words from rival fans and media in both countries. Now Australians are wondering if a cyber-attack that took down the country’s first attempt to conduct an online census is the latest front in this sporting war. And elsewhere online, the website of Swimming Australia was operating in ‘under attack’ mode after also seemingly being hit. WATCH: golden moments on Day 5 at the Rio Olympics The Australian Bureau of Statistics, which conducts the census, finally got its website back online on Thursday after it was out of action for 43 hours because of cyber-attacks. And a cyber-security expert in Australia said “it’s not way out of left field [as a motivation]” that Sun’s fans – angry over Horton’s repeated claims that the Chinese swimmer is a drug cheat – could have been behind it. Suelette Dreyfuss made the claim in an interview with the Sydney Morning Herald. She said the DDoS attack – where a website is swamped with traffic from ‘bots’ to take down the server – seemed too “noisy” and unsubtle to be the work of professionals. “If they wanted to get the data, particularly a powerful state actor, they’re likely to do it quite quietly because they don’t want anyone to know that they’re there,” Dreyfuss told the SMH. WATCH: relive the action involving Hong Kong athletes on Day 4 and Day 5 at the Rio Olympics Millions of Australians could not take part in the census because the site was down. And furious politicians are calling for a state-level inquiry into the fiasco. “It was an attack, and we believe from overseas,” the ABS’s chief statistician David Kalisch told ABC NewsRadio. He said the site had been attacked four times and was eventually taken down by the ABS to protect it. Kalisch made a grovelling apology to the people of Australia, ensuring them their data was safe. But Prime Minister Malcolm Turnbull has signalled that heads will roll over the debacle. “This has been a failure of the ABS. We have inconvenienced or the ABS has inconvenienced millions of Australians,” he said. “It shouldn’t have happened. I am not happy about it. None of us are. We are very disappointed.” The attack appeared to come from US servers, but Turnbull pointed out that it was straightforward to redirect traffic through the US. Meanwhile, Australian Broadcasting Corporation said the attack on Swimming Australia’s website had been referred to the government for investigation. While the site continues to function, it has been using a browser check to ensure visitors are legitimate. Chinese netizens have been rushing to Sun’s defence online, bombarding Horton’s social media pages with abuse.