Masimo Cyberattack Investigation | Data Breach Lawyers

The data breach lawyers at The Lyon Firm are investigating a cyberattack reported at Masimo Corporation that may have compromised a large amount of sensitive personal data. An investigation is still ongoing and data breach notification letters have not yet been sent to impacted individuals. Contact our legal team to learn more about filing class action data breach lawsuits and to take the next steps in protecting your personal information.

What Happened at Masimo?

On April 27, 2025, Masimo Corporation, a large medical technology company, identified unauthorized activity on its company network. According to a disclosure filed with the U.S. Securities and Exchange Commission (SEC), Masimo detected the security breach and called in cybersecurity experts to assist with the investigation and incident response.

In response to the incident, Masimo released a statement in an SEC filing, which reads: “As a result of the incident, certain of the Company’s manufacturing facilities have been operating at less than normal levels, and the Company’s ability to process, fulfill, and ship customer orders timely has been temporarily impacted.”

This data security incident apparently impacted Masimo’s manufacturing facilities, and the company is still working to restore affected portions of its network. The full scope and nature of the breach are still under review, and the company currently says that its cloud-based systems were not affected.

On the dark web, a threat actor known as “almighty4444” claimed responsibility for the attack and posted a sample of allegedly stolen data on September 2, 2024. The stolen information reportedly includes 61 MB of user data, including personally identifiable information (PII).