U.S. Department of Defense Data Breach History

This page tracks the U.S. Department of Defense data breach history and cybersecurity incidents affecting U.S. Department of Defense (United States). BreachHistory currently indexes 3 publicly disclosed or catalogued incidents spanning 2006 through 2009, with approximately 86 thousand records reported as exposed across all indexed events. These totals may include overlapping datasets or third-party estimates and should not be interpreted as unique affected users.

The U.S. Department of Defense breach timeline includes major data breaches, cyber attacks, data leaks, credential exposures, API abuse, and other security incidents. Each incident provides details on the estimated records exposed, attack method, affected data types, and supporting public sources. Currently, 0 incidents are company-confirmed.

Largest U.S. Department of Defense Data Breaches

The largest indexed incidents include the 2009 — U.S. Department of Defense: Lost / stolen device, 72000 records and the 2006 — U.S. Department of Defense: A hacker accessed a Tricare Management Activity…. Record counts originating from threat actors or leak sites should be treated as estimates unless confirmed by U.S. Department of Defense or a regulator. Below is the list of large data breaches:

• 2009 2009 — U.S. Department of Defense: Lost / stolen device, 72000 records — about 72.0K records exposed · Catalogued incident
• 2006 2006 — U.S. Department of Defense: A hacker accessed a Tricare Management Activity… — about 14.0K records exposed · Catalogued incident

What Information Was Exposed?

Depending on the incident, exposed data may include email addresses, names, physical addresses, health and medical (PHI) records, and other personal information (PII). The exact data varies between incidents, so review each breach page before assuming your information was affected.

U.S. Department of Defense Data Breach 2026

At the time of this update, no U.S. Department of Defense data breach has been catalogued for 2026. New incidents are added as official disclosures, regulatory filings, or credible cybersecurity reports become available.

What To Do If You Were Affected

If you believe your account may have been involved in a U.S. Department of Defense data breach, change any reused passwords, enable multi-factor authentication (MFA), monitor your account for suspicious activity, and be cautious of phishing emails or fake breach notifications.

This U.S. Department of Defense breach history is maintained by BreachHistory using public disclosures, regulatory filings, security research, and clearly labelled third-party claims. For the complete breach timeline, records exposed, incident details, and AI Breach Risk Score, explore the sections on this page.