On April 8, 2025, Eisner Advisory Group LLC filed a notice of data breach with the Attorney General of Montana after discovering that an unauthorized party was able to access parts of the company’s computer network. In this notice, EisnerAmper explains that the incident resulted in an unauthorized party being able to access consumers’ sensitive information, which includes their names, addresses, Social Security numbers, driver's license numbers, state-issued identification numbers, passport numbers, dates of birth, financial account information, payment card information, medical information, and health insurance information. Upon completing its investigation, EisnerAmper began sending out data breach notification letters to all individuals whose information was affected by the recent data security incident.
If you received a data breach notification from Eisner Advisory Group LLC, it is essential you understand what is at risk and what you can do about it. A data breach lawyer can help you learn more about how to protect yourself from becoming a victim of fraud or identity theft, as well as discuss your legal options following the EisnerAmper data breach. For more information, please see our recent piece on the topic here.
What Caused the EisnerAmper Data Breach?
The EisnerAmper data breach was only recently announced, and more information is expected in the near future. However, EisnerAmper’s filing with the Attorney General of Montana provides some important information on what led up to the breach. Eisner Advisory Group also posted a website notice discussing the breach.
According to these sources, in September 2023, EisnerAmper detected suspicious activity related to certain information in the company’s possession. In response, EisnerAmper launched an investigation to learn more about the incident and whether any consumer information may have been compromised.
Through this investigation, EisnerAmper confirmed that an unauthorized party had accessed its network between September 4, 2023 and September 23, 2023, including files containing confidential consumer information.
After learning that sensitive consumer data was accessible to an unauthorized party, EisnerAmper reviewed the compromised files to determine what information was leaked and which consumers were impacted. EisnerAmper completed this process in February 2025. While the breached information varies depending on the individual, it may include your name, address, Social Security number, driver's license number, state-issued identification number, passport number, date of birth, financial account information, payment card information, medical information, and health insurance information.
On April 8, 2025, EisnerAmper sent out data breach letters to anyone who was affected by the recent data security incident. These letters should provide victims with a list of what information belonging to them was compromised.
More Information About Eisner Advisory Group LLC
EisnerAmper LLP is a full-service accounting and advisory firm offering audit, tax, advisory, and consulting services to clients across various industries. Headquartered in New York City, the firm operates multiple offices throughout the United States and internationally. EisnerAmper serves a diverse clientele, including corporations, not-for-profit organizations, and high-net-worth individuals, providing specialized services in areas such as financial services, real estate, healthcare, and technology. The organization employs approximately 4,000 people and generates an estimated $472 million in annual revenue.
