Japanese sportswear company Mizuno confirms data breach after 2024 ransomware claims

Customers of Japanese sportswear company Mizuno had information stolen during a cyberattack last year that was claimed by a ransomware gang.

The company reported the breach to regulators in Maine on Thursday but would not say how many people were affected by the incident, leaving that section of the form blank. The company did not respond to requests for comment about the issue.

Mizuno initially discovered malicious activity on its network on November 6 before launching an investigation that revealed hackers had been in their systems since at least August 21 and had copied files “periodically.”

Most customers had names, Social Security numbers, driver’s license numbers, and financial account information stolen during the incident. Victims are being given one year of identity protection services.

The Osaka-based company reported nearly $1.4 billion in net sales in the last fiscal year. In addition to sportswear like sneakers, the company produces equipment for a variety of sports. 

The filing in Maine does not specify the exact nature of the attack, but the incident was claimed by the BianLian ransomware group on November 11. The cybercriminals shared evidence that allegedly includes financial data, human resources records, vendor contracts and more. 

The FBI published a warning about the group in November after a string of high-profile attacks, writing that the gang’s key operators and affiliates are likely based in Russia.

BianLian has drawn scrutiny for attacks on charities like Save The Children as well as healthcare firms like Boston Children’s Health Physicians.

The advisory notes that like many ransomware gangs, the likely Russia-based group has used its name “to misattribute location and nationality by choosing foreign-language names, almost certainly to complicate attribution efforts.”