The Pentagon’s Defense Manpower Data Center (DMDC) is notifying millions of military service members that hackers stole their data after breaching the Pentagon’s human resources management system in October 2025.

In data breach notification letters shared online by affected individuals, the DMDC told affected military personnel that “a small number of unauthorized users” had access to their sensitive data, including personally identifiable information (PII), between October 2025 and July 2026 after exploiting a vulnerability in its file-sharing systems.

The stolen data varies by person and includes Social Security numbers (SSNs), names, dates of birth, contact information, sex, race, and military personnel information.