A 31-year-old was recently booked by the police for infiltrating the accounts of 25 million people on Naver, the nation’s largest Web portal.

According to the National Police Agency on Wednesday, the suspect, surnamed Seo, purchased the private information of 25 million people from a Korean-Chinese in August this year.

Seo then used the data, which included the names, residential numbers, Internet IDs and passwords, to hack into Naver accounts.

He sent spam messages and other illicit emails to the Naver account holders to rake in illegal profit of some 160 million won ($148,000).

The police also caught a self-taught computer programmer surnamed Hong who had developed hacking programs including ones that automatically enter IDs and passwords to log in to Naver.

The information extracted this way was also supplied to Seo.

The police also indicted three accomplices of Seo without detention, and said it is expanding its investigation into 86 others who bought the computer programs made by Hong.

A Naver official said it was not able to prevent such attempts at accessing and abusing data from outside sources.

He added that the best preventive measure for now would be for users to change their passwords on a regular basis so that even if someone should access their accounts the impact would be minimal.

Further, he stressed that Naver was not at fault regarding the incident, adding that a bigger problem was that it was too easy for people to get their hands on the personal information of others.

By Kim Young-won (wone0102@heraldcorp.com)