DHS Investigates Cyber Breach of Homeland Security Network

The U.S. Department of Homeland Security (DHS) is investigating a cyber breach involving the Homeland Security Information Network (HSIN), according to a Reuters report published Sunday.

The HSIN platform is used by federal agencies, state and local governments, law enforcement, and private-sector partners to share sensitive but unclassified information.

According to the initial investigation, the breach likely occurred between the end of May and the beginning of June. The attackers, whose identities have not yet been determined, reportedly gained access to the network's servers and the SharePoint collaboration system.

The Senate Intelligence Committee warned that although the compromised information is not classified, it is highly sensitive and its exposure could pose risks to national security. The HSIN platform is also used to coordinate security for major national events, including the 2026 FIFA World Cup.

According to the report, officials are concerned that emergency response plans and other security procedures may have been exposed. The Department of Homeland Security said the affected systems have been isolated and that a comprehensive forensic investigation is underway to determine the full scope of the breach.

In a statement, the U.S. Department of Defense said that "a cyber incident recently occurred involving a legacy unclassified information-sharing environment." The department did not provide additional details.