DHS Confirms Breach of Information-Sharing Network Platform HSIN

The Department of Homeland Security confirmed that an unknown threat actor gained unauthorized access to the Homeland Security Information Network (HSIN) — a sensitive but unclassified information-sharing and collaboration platform — sometime between late May and early June 2026, impacting HSIN servers and a SharePoint system; DHS isolated affected systems, is conducting a forensic damage assessment, and reports no indication that classified networks were impacted.