Hamill & Kaplan, LLP, a law firm based in Westlake Village, California, has notified clients that an unauthorized user gained access to its computer network, potentially exposing sensitive personal information. Law firms handle a significant volume of clients’ sensitive financial and identifying information, and are expected to maintain reasonable safeguards to keep that data secure.
Hamill & Kaplan’s Data Breach Investigation
According to a notification letter filed with the California Attorney General’s Office, Hamill & Kaplan discovered on September 19, 2025 that an unauthorized user had gained access to its computer network earlier that same day. The firm stated that the threat actor was able to access some of its files, which included clients’ personal information. Hamill & Kaplan said it has no information indicating that the exposed data has actually been misused, but it is notifying affected individuals so they can take proactive steps to protect themselves.
Following discovery of the incident, the firm said it took immediate measures to secure its network and began an investigation with the assistance of third-party IT specialists to determine the full nature and scope of what occurred. Hamill & Kaplan also stated that it notified the FBI, the IRS, California’s Franchise Tax Board, and the U.S. Secret Service about the incident, and that notification to affected individuals was not delayed as a result of any law enforcement investigation.
Law firms are increasingly attractive targets for cybercriminals because they routinely store sensitive client records, including Social Security numbers, financial account details, and confidential case files, often for extended periods of time. When this type of data is compromised, affected individuals can face an elevated risk of tax fraud and identity theft, particularly given that the firm specifically warned clients to watch for suspicious activity tied to their tax returns.
The notification letter did not disclose how many individuals were affected nationwide or in California specifically. Hamill & Kaplan reported the incident to the California Attorney General’s Office on August 6, 2026, nearly eleven months after the incident was first discovered, which the firm attributed in part to the time needed to complete its forensic investigation.
When Did This Breach Occur?
Hamill & Kaplan discovered the unauthorized access on September 19, 2025. The firm’s notification letter to affected individuals is dated August 3, 2026, and the incident was reported to the California Attorney General on August 6, 2026.
What Information Was Breached?
Per Hamill & Kaplan’s notification letter, the information that may have been accessed includes clients’ Social Security numbers, other government-issued identification numbers, names, bank account information, and other sensitive information clients may have provided to the firm.
What You Can Do
If you received a notice from Hamill & Kaplan or believe you may have been affected by this breach, consider taking the following steps:
- Monitor your bank accounts and tax records closely for any suspicious activity.
- Watch for notices from the IRS regarding potential fraudulent activity connected to your tax return.
- Consider enrolling in any credit monitoring services offered by the firm.
- Place a fraud alert or credit freeze with the major credit bureaus as a precaution.
- Keep any notification letter you received, as it may serve as documentation if you decide to pursue legal action.
File a Data Breach Lawsuit Against Hamill & Kaplan
If your personal information was compromised in the Hamill & Kaplan data breach, you may have legal options available to you. Law firms that collect and store sensitive client information have a responsibility to protect it with reasonable security measures.
Contact us at Class Action U, where we’ll connect you with a lawyer skilled in class action lawsuits. If you’ve been contacted about this breach, received notice, or discovered you were impacted, fill out our quick, easy, and secure form to sign up. There is no cost to reach out to our legal partner and no obligation after speaking with someone from our team.
