US Government Investigates Fresh Cyberattack on Homeland Security Network

The US Department of Homeland Security is investigating a cybersecurity breach involving one of its information-sharing platforms used by federal, state, and local governments, as well as law enforcement agencies. A senior lawmaker has warned that the incident could expose highly sensitive information and pose risks to national security.

According to reports from Nextgov, which first revealed the incident, and BleepingComputer, DHS officials are examining a cyberattack targeting the Homeland Security Information Network (HSIN). The platform enables government agencies and local officials to coordinate operations, exchange intelligence, prepare for major events, and respond to emergencies.

The reports indicate that attackers gained access to HSIN servers sometime between late May and early June, potentially exposing information that had been shared through the system.

In an emailed statement, a DHS spokesperson, who was not identified by name, confirmed that the department is “aware of a recent cyber incident involving a specific, unclassified legacy information sharing environment.”

The spokesperson added, “We immediately took action to isolate the affected systems, mitigate the vulnerability, and launch a comprehensive forensic investigation.” DHS also said the investigation remains active and declined to provide additional details.

At this stage, it is not known what information may have been compromised or how much data was accessed. A separate security issue disclosed in 2023 had already shown that HSIN stored personal information exchanged among law enforcement agencies related to surveillance activities involving Americans.

The latest incident places renewed attention on the federal government’s ability to secure its own digital infrastructure. It comes after more than a year of significant staffing and budget reductions across several federal agencies, including the Department of Homeland Security and the Cybersecurity and Infrastructure Security Agency (CISA), during the Trump administration.

Although the intelligence exchanged through HSIN is not classified, Senator Mark Warner, the Democratic ranking member of the Senate Intelligence Committee representing Virginia, said the information remains highly sensitive and that its exposure could create national security concerns.

Warner noted that HSIN is currently supporting security coordination for the World Cup matches taking place across the United States. He also said the platform was used last year during the emergency response to the mid-air collision involving an American Airlines passenger jet and a US Army Black Hawk helicopter near Washington, D.C. This accident claimed the lives of 67 people.

Authorities have not identified who was responsible for the attack, nor have they disclosed the hackers’ affiliations or motives. However, the breach represents the latest in a series of cybersecurity incidents affecting the US federal government over the past year.

Since the Trump administration took office in January 2025, multiple security lapses have drawn attention, including the sharing of classified information and military plans through messaging applications such as Signal that were not authorised for government use, the reported access of federal databases containing Americans’ personal information by members of Elon Musk’s Department of Government Efficiency (DOGE), and the accidental exposure of large numbers of passwords and credentials by a CISA contractor, which reportedly provided access to government cloud systems.

Earlier this year, the FBI also informed members of Congress that it had declared a “major cyber incident” after inadvertently exposing the phone numbers of individuals under federal surveillance, a disclosure that could have given those targets an operational advantage.