SINGAPORE - Singtel is still investigating the root cause of a fibre broadband outage that saw its users cut off from Web surfing for 3½ hours on Wednesday (July 4) morning, but the telco has ruled out a cyber attack.

The telco notified customers of the disruption via a Facebook post around 9am, saying its engineers were investigating the problem. At 11am, the telco said Internet access was restored.

During the outage, even online payments provider AXS’ website and app, which run on Singtel’s fibre broadband network, could not be accessed.

The Infocomm Media Development Authority (IMDA) said on its Facebook page that it has started its own investigations into the outage.

Users started complaining online as early as 7.30am, reporting outage in areas as far and wide as Choa Chu Kang, Tampines, Woodlands, Jurong, Bedok, Thomson, Tiong Bahru, Holland Avenue, Toa Payoh, Bukit Panjang, Katong, Marine Parade, Hougang, Queenstown and Punggol.

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Singtel’s website was not accessible for several hours but access was restored at around 11am. At 10.55am, the telco posted an update on its Facebook page, saying that Internet access for residential customers was being “progressively restored”.

A domain name system (DNS) error message also appeared when accessing e-payment service provider AXS’ website. DNS maps Web addresses to a machine-readable string of numbers to connect Internet users to websites.

The error message read: “Your request could not be processed because an error occurred contacting the DNS server. The DNS server may be temporarily unavailable, or there could be a network problem.”

Mr Chin Mun Chung, AXS assistant chief executive told The Straits Times that it was made aware of the outage on its website and app at around 7.40am.

Service was restored at 11am, he said, noting that the physical AXS stations were not affected by the outage.

The outage has brought about inconvenience to users such as Mr Jamie Khoe. “Due to the Internet outage, I was unable to continue with my online leisure activities. I am quite disappointed with Singtel because... they provided very little information about why there was an outage,” said the 25-year-old digital marketer.

Software engineer Zhang Xuanrong, 27, said that after realising Singtel’s DNS was down, he switched to Google’s DNS. “It worked for me after that.”

University student Howard Wong, 23, was trying to register for a course, which was on a first come, first served basis, when he could not access the Internet. “In the end, I was not able to secure an important module and might have to take it next semester (instead of this semester).”

Ms Deborah Kek, 19, a polytechnic student currently on an internship, said: "I wanted to access my messages and I couldn't. It also affected me as I was awaiting an important e-mail from work. I am quite frustrated because this isn't the first time I had connectivity issues with Singtel."

School work for some students was affected.

A senior marketing specialist, who wanted to be referred to only as Ms Di, 40, had taken leave to help her son with his home-based learning assignments. “I restarted the router at least five times, but each time, it worked less than five minutes and would go down again.”

Said Ms Tan Li Yan, 19, a polytechnic student: "I had to get some school work done, but I couldn't do so because the Internet was down. I am very disappointed as Singtel is not giving the service we paid for."

Khoo Qi En, 18, a student of Eunoia Junior College, said: "I was trying to do a Google search for an article and look for a video on YouTube but they would not load."

Polytechnic student Tiffany Lam, 18, could not load her social media platforms. "I couldn't receive notifications. It's annoying to have the house Wi-Fi not work, it's really inconvenient."

Mr Aloysius Cheang, Asia-Pacific executive vice-president of the Centre for Strategic Cyberspace + Security Science, a London-based think-tank, said: “Singtel’s network could have been overwhelmed by heightened use of certain applications such as virtual private networks (VPNs) and online gaming access as a result of the World Cup.”

Besides being used to secure corporate networks, VPN technologies are also used by some people to access blocked or illegal content.

In October last year, Singtel was fined $500,000 for a massive 24-hour islandwide fibre broadband outage in 2016 that left about 490,000 users cut off from the Web.

Additional reporting by Jasia Shamdasani