2026 Kiewit Corporation — Microsoft 365 account compromise; employee/contractor SSNs and health data
Data compromised
Names, addresses, dates of birth, Social Security numbers, driver’s license numbers, government-issued identifiers, and employment-related health information for current/former employees and independent contractors (varied by individual)
Technical writeup
Verified company notice via Massachusetts AG filing — reported August 21, 2026. Kiewit Corporation, a major North American construction and engineering firm, detected unauthorized access to an employee’s Microsoft 365 account and engaged third-party forensics. Review completed July 24, 2026 found data that may include names, addresses, DOBs, SSNs, driver’s licenses, government IDs, and health information tied to employment for current and former employees and independent contractors. Kiewit had not published a nationwide headcount at indexing; recordsAffected 0 pending census; companyConfirmed true.
Root cause
Unauthorized access to an employee Microsoft 365 account; forensic review concluded July 24, 2026 per Massachusetts AG notice
References
- https://www.classaction.org/data-breach-lawsuits/kiewit-corporation-august-2026
- https://www.prnewswire.com/news-releases/kiewit-corporation-data-breach-alert-edelson-lechtzin-llp-investigates-exposure-of-employee-and-contractor-personal-information-302860992.html
- https://www.mass.gov/doc/data-breach-report-2026/download