The massive leak last month of personal data from the Japan Pension Service was the result of a simple error by its employees: opening a virus-laced email attachment disguised as a health ministry document.
Hackers who tapped into the pension system and stole the data of 1.25 million people are believed to have used a classic ploy called a "targeted email attack." It's been around since around 2003 overseas and 2005 in Japan, but has become more sophisticated in recent years, with the email giving every appearance of containing legitimate and important business, experts say.
Police know of 1,723 targeted email attacks in 2014, up from 492 in 2013 and 1,009 in 2012, according to the National Police Agency.