South Korean Telco KT Suffers Nationwide Outage After Routing Error

The second-largest telecommunications provider in South Korea, KT Corporation, has suffered a nationwide outage today, leaving all its 16.5 million customers without internet connectivity and telephony services for about 40 minutes.

The outage affected schools and students who attended online classes, delayed food delivery orders, prevented physicians from accessing patient data, and disrupted credit card processing in stores.

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A team of investigations from the Seoul cyber department was dispatched to KT’s headquarters to support the telco in whatever problem they were facing.

While the scenario of a DDoS (distributed denial of service) attack was communicated as the most likely cause of the problem initially, the firm later explained that it was a routing error that took its services down.

Faulty routing configurations can be catastrophic, as we saw in a recent BGP routing issue that caused significant downtime for Facebook, Instagram, and WhatsApp.

KT fixed this issue in 40 minutes but has not provided a reason for the outage at this time and is still investigating it. However, it is believed that a BGP configuration error caused the outage.

“We are promptly responding to the situation by operating the firm’s risk management committee. We will do our best for quick recovery,” KT told local media outlets.

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BGP routing errors prevent data packets from reaching intended IP addresses and servers, causing a service disruption even though the services themselves are still up and running.

Interestingly, phone call problems in some regions persist, and it’s unclear why these locations are still facing problems.

The short outage on KT caused a sudden overload on Korea’s two other major telcos, SK Telecom and LG Uplus, whose users experienced service interruptions and hiccups as a result.

This created some confusion around the nature and scale of the problem, but soon, the IT Ministry clarified that neither company is dealing with any DDoS attacks at the moment.

The last time KT’s customers suffered from a major outage was in 2018, when a fire broke at its Ahyeon branch in Seoul, disrupting the services in the South Korean capital for days and forcing the firm to reimburse customer subscriptions.