The Department of Homeland Security (DHS) is investigating a cyber intrusion involving the Homeland Security Information Network (HSIN), according to a Nextgov/FCW report. HSIN is a key platform used to share sensitive but unclassified information among federal, state, local and private-sector partners.

The breach is believed to have occurred between late May and early June, with investigators examining unauthorized access to HSIN servers and a SharePoint-based collaboration environment. Officials have not identified the threat actor responsible, and it remains unclear whether any information was stolen.

DHS’s Office of Intelligence and Analysis has reportedly conducted a damage assessment as part of the ongoing investigation. HSIN is widely used for secure information sharing, incident response coordination, event security planning, operational management, and communication among government agencies and critical infrastructure partners.

The incident comes as U.S. authorities continue to oversee security operations for FIFA World Cup events hosted across the country, raising concerns about the potential exposure of planning and coordination information tied to major public events.

In a statement, DHS said it had isolated affected systems, mitigated the vulnerability and launched a forensic investigation. The department emphasized that there is no indication classified networks were compromised and that the platform remains operational.

House Homeland Security Committee staff recently requested a briefing from the Department of Homeland Security regarding the breach of the Homeland Security Information Network, according to a committee aide familiar with the matter.