Computer viruses and people accessing databases without authorization have led to the compromise of personal information belonging to 8.9 million workers and customers of 32 publicly traded companies in Japan last year, a private credit research firm said Thursday.

The number of affected companies hit a record high since the survey began in 2012, Tokyo Shoko Research Ltd. said.

Most recently, Mitsubishi Electric Corp. said that a cyberattack exposed personal information on 8,000 people.

There may have been more affected companies as some cases have gone unnoticed, Tokyo Shoko Research said.

Personal information on 9.03 million people was compromised at 66 publicly traded companies in the country last year. The bulk of the cases were caused by viruses and people accessing information without authorization.

More hackers are stealing customers’ usernames and passwords as the number of companies operating e-commerce sites are increasing.

The largest known case of a data breach last year occurred at Ogis-Ri Co., a file transfer service unit of Osaka Gas Co., where personal information on 4.81 million users was exposed.

“Hackers are overtaking companies’ security efforts,” a Tokyo Shoko Research official said.