<Anchor> It was

confirmed that the paralysis of KT's internet network that occurred last Monday was caused by omitting a single command word while replacing equipment.

Although it started as a work error, KT did not have a system to prepare for such an accident, and there were many problems with the work procedure.

Reporter Han Sang-woo reports.

<Reporter> The

nationwide KT Internet network paralysis started with the replacement of network path setting equipment at KT Busan National Office.

[Cho Kyung-sik / Vice Minister of Science and Technology Information and Communication: The worker entered an incorrect setting command, and it was analyzed that a nationwide Internet failure occurred later due to a routing error.]

When the command called "Exit to terminate the job and exit" was omitted, tens of thousands of unnecessary data attached to it were rushed to the router.

As this data spread across the country, traffic increased four times more than usual, and the network was paralyzed.

[Seung-Joo Kim / Professor, Graduate School of Information Security, Korea University: Routers started creaking because they had to update a large amount of information (than usual), and as they spread across the country, all route information changes.

In the meantime, the nationwide network was down.]

KT did not have a testing process after the replacement work, nor did it have a system to block the spread of local errors across the country.

At the site of replacing important equipment, KT entrusted only the employees of the subcontractors without the manager.

Above all, the decisive cause of the damage was that the work that was originally scheduled from 1 am to 6 am was carried out during the daytime.

KT promises to prevent recurrence and offers a compensation plan that goes beyond the terms of compensation only when a failure occurs for more than 3 hours, but has not revealed any specific plans yet.

(Video coverage: Jeong Seong-hwa, video editing: Kim Jun-hee)