An IT worker was arrested after allegedly copying names, Social Security numbers, and credit card details of 20 millions South Koreans to a USB stick, so the trove of information could be sold to phone marketing firms.

According to a Monday BBC News article, the IT worker under suspicion worked for the Korea Credit Bureau.

In response to the breach, top executives at three credit card firms impacted by the incident – KB Kookmin Card, Lotte Card, and Nonghyup Card – made a public apology and resigned from their positions.

The contractor suspected of stealing the information is thought to have obtained the data through the Korea Credit Bureau's access to the credit card companies' databases.