Case file: MKS Instruments, Inc. (“MKSI")
Every government filing on this incident, the dates as stated, and the days to notice against each state's statute. Built from the records on Nov 9, 2026, agency link on every row. Not legal advice.
The incident
- Breach window
- Not stated in the filings
- Discovered
- Feb 16, 2023, as stated in the California letter
- State and federal records
- 1 filing, Feb 15, 2023
- Residents counted
- No state publishes a resident count for this incident
- Everyone affected
- No filing gives a total
- Information exposed
- Social Security number, Financial / bank account, Medical / health information, Health insurance, Date of birth, Usernames / passwords, Postal address
- Offered to those affected
- 24 months of credit or identity monitoring through Experian
- Third party named
- No
The letter: "MKS Instruments, Inc. 2 Tech Drive, Suite 201 Andover, MA 01810 United States February 16, 2023 1 NOTICE OF DATA BREACH We are contacting you because we recently became aware of a security breach that may have resulted in the unauthorize..."
Filings
| Agency | Record date | People | In total | Days to notice | Links |
|---|---|---|---|---|---|
| California California AG | Feb 15, 2023 | Not published | No dates to count between | Letter Record |
People is the count the filing gives, residents of the state unless marked total. Days to notice runs from the discovery date the letter states, or from the end of the breach window when no letter states one, to the date on the state's first record of the incident. "Over" marks a count past the days the state's statute allows for notice to residents. The statute's trigger is a question of fact, the days are arithmetic.
The statutes
- California: 30 days to notify residents from discovery or notification of the breach, Cal. Civ. Code § 1798.82. Sample notice to the Attorney General when more than 500 Californians are notified, within 15 days of the consumer notice (effective 2026).
Sources and method
Records as published by California AG. Letter facts (discovery date, monitoring, third party) are read from the consumer letter the agency posted, 1 letter read for this incident, and quoted so you can check them. Texas and HHS publish no letters. First-seen times on each record page. Spot an error? Email support@breachtally.com with this page link.