The Los Angeles County Museum of Art (LACMA) says a data breach last year exposed customer and employee information, including medical and social security data. The museum has begun sending personalized notifications to people affected after an investigation into the incident, which began during the summer of 2025. LACMA said it detected suspicious activity on its systems on July 11, 2025. Its investigation found that the activity had started four days earlier, on July 7. A month later, the museum confirmed that its network had been compromised. Although LACMA confirmed the network compromise last summer, it said it could not then determine the types of data that had been exposed. The first results of the investigation became available in late February 2026, giving the museum more information about the data affected by the incident. The museum has notified law enforcement authorities and sent personalized breach-notification letters to impacted individuals. It has not publicly disclosed the number of people affected. BleepingComputer contacted LACMA with questions about the number of affected individuals and the nature of the attack, but said it had not received a response by publication. LACMA recommends that recipients of the letters monitor their bank accounts for suspicious activity. It also advises affected people to consider placing a security freeze or fraud alert on their credit files, and to report identity-theft attempts to their financial institutions and law enforcement. The notification letters include information about enrolling in a one-year identity-theft and fraud-protection service provided through Financial Shield. The enrollment deadline is November 22. LACMA has also set up a dedicated telephone line to provide support and answer questions from people affected by the breach. LACMA is among the largest art museums in the western United States. Its collection contains around 155,000 works spanning 6,000 years of art history, and the museum has historically attracted more than one million visitors each year. A letter in the post and an unexpected credit-file alert can be the first practical signs that a person needs to act. Somali diaspora members in Southern California who visited, bought tickets from, or worked for LACMA can check any notification they receive and follow the steps in it if they are identified as affected.