The incident on Oct 8 last year affected more than 500,000 users for more than four hours
[SINGAPORE] The Infocomm and Media Development Authority (IMDA) imposed a S$1 million fine on Singtel for a 2024 voice disruption, it said on Thursday (Dec 11).
The October incident last year affected about 500,000 of Singtel’s residential and corporate users for more than four hours, noted IMDA.
“The public’s access to customer service lines for some government agencies, healthcare organisations, banks and companies, and emergency call services was also affected,” said the statutory board.
Singtel Singapore chief executive Ng Tian Chong accepted IMDA’s ruling and the financial penalty.
“We recognise the seriousness of the disruption to our fixed voice service last October,” he said. “I would like to express my sincere apologies once again for the disruption and inconvenience experienced.”
In determining the financial penalty, IMDA noted that it considered the scale and impact of the disruption, as well as the time taken to restore the network.
It deemed the impact of the incident as “significant”, and said that the potential consequences on the safety and security of the public “could have been very serious”.
IMDA’s findings were supported by independent external consultants appointed. The authority’s investigation concluded that the incident was within Singtel’s control to prevent. It also determined that the incident was not due to a cyberattack.
Ng added: “Following the incident, we took immediate remediation action to prevent a re-occurrence of the incident by improving our network design and hardware configuration and enhancing our monitoring processes. We also worked with our clients to strengthen their customer service hotline resiliency.”
What caused the disruption
IMDA’s investigation found that Singtel hosted two separate virtualised firewalls on the same hardware. One was for its fixed-line voice system, and another for the monitoring system for home broadband routers and its pay TV set-top boxes.
This meant that both virtualised firewalls shared the same hardware memory resources.
As the monitoring system’s virtualised firewall did not have “adequate filters” installed to protect the hardware against high-intensity traffic, the shared memory resources of the hardware were overwhelmed when the monitoring system faced increased traffic intensity on Oct 8, 2024.
This caused the virtualised firewall of the voice system to also malfunction and operate intermittently.
Although voice traffic from the affected voice system should have been seamlessly redirected to a separate voice system at an unaffected site, the intermittency of the affected voice system’s virtualised firewall prevented this from happening.
As a result, calls were dropped intermittently as voice traffic alternated between the affected and unaffected voice systems. The incident was resolved only after Singtel fully moved all voice traffic to the unaffected voice system.
IMDA added that it holds telcos which are key service providers, such as Singtel, to a “high level of service reliability”.
“IMDA will not hesitate to take strong action under the Telecommunications Act, including imposing financial penalties,” said the statutory board. “Under the Telecommunications Act, IMDA may impose a penalty of up to S$1 million or up to 10 per cent of their annual turnover.”
In the 2025 financial year ended March, Singtel posted a S$14.1 billion operating revenue. It returned to the black in the second half-year with a net profit of S$2.8 billion.
In September, an emergency service outage by Singtel subsidiary Optus resulted in the death of three people in Australia. That was followed by a less-impactful Singtel mobile outage on Nov 18, with more than 1,600 reports on Downdetector in the afternoon.
Shares of Singtel ended Thursday 0.4 per cent or S$0.02 lower at S$4.56, before the fine was announced.
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