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Advantest Discloses Data Breach Months After Ransomware Attack

Securityweek •Eduard Kovacs • October 7, 2026

Japanese chip testing giant Advantest is informing individuals that hackers stole personal information in the ransomware attack disclosed in February 2026. Advantest, which makes automatic test equipment for chipmakers such as Intel and Samsung, said in February that hackers had breached its network and deployed ransomware. At the time, it was still working to determine whether any sensitive information had been exfiltrated. In data breach notifications sent out now, the company said the attackers stole personally identifiable information, including names, dates of birth, information, SSNs, passport and driver’s license numbers, and medical and financial information. “We have no information suggesting that your PII has been disclosed publicly or otherwise misused,” Advantest said. “However, this incident may have placed you at increased risk of identity theft or fraud.” The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Advantest, which makes automatic test equipment for chipmakers such as Intel and Samsung, said in February that hackers had breached its network and deployed ransomware. At the time, it was still working to determine whether any sensitive information had been exfiltrated. In data breach notifications sent out now, the company said the attackers stole personally identifiable information, including names, dates of birth, information, SSNs, passport and driver’s license numbers, and medical and financial information. “We have no information suggesting that your PII has been disclosed publicly or otherwise misused,” Advantest said. “However, this incident may have placed you at increased risk of identity theft or fraud.” The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

At the time, it was still working to determine whether any sensitive information had been exfiltrated. In data breach notifications sent out now, the company said the attackers stole personally identifiable information, including names, dates of birth, information, SSNs, passport and driver’s license numbers, and medical and financial information. “We have no information suggesting that your PII has been disclosed publicly or otherwise misused,” Advantest said. “However, this incident may have placed you at increased risk of identity theft or fraud.” The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

In data breach notifications sent out now, the company said the attackers stole personally identifiable information, including names, dates of birth, information, SSNs, passport and driver’s license numbers, and medical and financial information. “We have no information suggesting that your PII has been disclosed publicly or otherwise misused,” Advantest said. “However, this incident may have placed you at increased risk of identity theft or fraud.” The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

“We have no information suggesting that your PII has been disclosed publicly or otherwise misused,” Advantest said. “However, this incident may have placed you at increased risk of identity theft or fraud.” The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

The company has not disclosed how many individuals were impacted by the data breach, but its filing with the California Attorney General’s Office indicates that more than 500 California residents are affected. Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Notifications submitted to attorneys general in Massachusetts and Vermont list 14 and 8 affected residents, respectively. No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

No known ransomware group appears to have taken credit for an attack on Advantest. Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Related : ASOS Confirms Cyberattack, Data Breach Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Related : Personal Information for Over 1 Million People Stolen in a Cyberattack on Arizona’s Court System Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Related : 8.8 Million Impacted by Data Breach at Denmark’s Central Person Register Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Related : 250,000 Impacted by Data Breaches at New Jersey, Texas Healthcare Firms

Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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Advantest Confirms Data Breach Following February Ransomware Attack Advantest, a Japanese semiconductor testing company, has disclosed that personal information was stolen during a ransomware attack in February 2026. The breach, which was initially reported in February, involved unauthorized access to its systems, with data including names, Social Security numbers, and financial information being compromised. Notifications sent to affected individuals on October 6, 2026, indicated that over 500 California residents were impacted, alongside smaller numbers in Massachusetts and Vermont. Advantest has not confirmed the total number of individuals affected or whether the data has been misused. The company is offering 18 months of free credit monitoring to those affected. No ransomware group has claimed responsibility for the attack, and the incident has been contained with the network restored. 6 sources 43

Extracted Entities

Advantest Discloses Data Breach Months After Ransomware Attack

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Extracted Entities

Attack Types (2)

Companies (1)

CWE Weaknesses (1)

MITRE ATT&CK (2)