Japan's pension system has been hacked and more than a million cases of personal data leaked, Reuters quotes authorities saying on Monday.
The embarrassment revived memories of a scandal that helped topple Prime Minister Shinzo Abe in his first term in office.
Japan Pension Service staff computers were infected with an external email virus, leading to the leak of some 1.25 million cases of personal data, the system's president, Toichiro Mizushima, told a hastily called news conference.
Names, ID numbers, birth dates and addresses were leaked, said Mizushima, apologizing for the leak.
He also said that the service was setting up an investigation team to make sure things like this one never happen again.
"These are the people's vital pensions. I have instructed Health and Welfare Minister (Yasuhisa) Shiozaki to consider the pension recipients and do everything possible," said Abe.
Separately, Shiozaki apologized for failing to prevent the hacking and told a news conference he had instructed the Japan Pension Service to set top priority on protecting the public's pensions.
Public outrage over botched record-keeping that left millions of pension premium payments unaccounted for was a major factor in a devastating defeat suffered by Abe’s Liberal Democratic Party in a 2007 election for parliament’s upper house.
Cyber security has become a major concern for many companies and governments, as cyber warfare enters the mainstream, and many companies suffer losses in the millions thanks to inefficient security measures.
Abe, whose first cabinet also lost several cabinet ministers to other scandals and gaffes, including one who committed suicide, resigned in September of that year in the face of parliamentary deadlock and ill health.