LG Uplus is moving to offer free USIM replacements and USIM resets for all customers. It is a supplementary measure following recent security concerns.

Industry sources said on March 17 that LG Uplus has been found to have used a method that combines subscribers' phone numbers when assigning the international mobile subscriber identity (IMSI) from 2011, the early days of LTE, to the present.

An IMSI is a 15-digit unique number stored on a USIM. It is used to identify users on a communications network. Unlike SK Telecom and KT, which assign it in a way that is difficult to predict using random numbers and other methods, LG Uplus used a method that combines phone numbers.

Security experts say that even if an IMSI value is leaked on its own, it does not immediately lead to hacking. They explain that it could lead to security threats if combined with other information.

LG Uplus will introduce randomisation of the IMSI system and support free USIM replacement and resets. LG Uplus has been carrying out system design and development, commercial verification and other work for a new IMSI system that randomises subscriber codes since June last year. When customers replace or reset their USIM, the system will be applied automatically.

LG Uplus will carry out USIM replacement and resets for all customers using its mobile phone services as of April 13. The programme will also include customers of secondary devices such as smartwatches, kids' phones and budget-phone users on the LG Uplus network.

After that date, customers who switch carriers or sign up as new subscribers will have the revised system applied automatically to new USIMs. It also plans to mandatorily apply 100 percent of the technology (SUCI) that encrypts IMSIs in 5G standalone (SA) mode, which will be commercialised this year.

LG Uplus said a detailed schedule related to USIM replacement and resets will be announced later. It also plans to operate a store visit reservation system to minimise waiting times at stores.

Lee Jae-won (이재원), head of the consumer division at LG Uplus and a vice president, said, "This application of a new security system is being carried out so that customers can use mobile communications services more safely." He said, "We will prepare to minimise inconvenience to customers during the application process."