Britain's Foreign, Commonwealth and Development Office suffered a cyberattack in October that prompted an investigation into the breach at one of the government's most security-sensitive departments, Resilience Media and the Financial Times reported on December 19.

Britain has faced sustained cyber pressure this year. The National Cyber Security Centre has flagged multiple "nationally significant" incidents hitting public institutions, critical infrastructure and large private companies. Jaguar Land Rover and Marks & Spencer both experienced attacks that disrupted operations.

Trade Minister Chris Bryant confirmed the intrusion this week, telling Sky News the department detected a "technical issue in one of our sites" and closed the vulnerability rapidly.

"There certainly has been a hack at the FCDO and we've been aware of that since October," Bryant said. "We're fairly confident that there's a low risk of any individual being affected by this."

The minister declined to identify those responsible when asked if a foreign state orchestrated the attack, stating: "That's not entirely clear."

Media reports have linked the breach to Storm 1849, a hacking group believed to operate on behalf of China.

The group has previously targeted government networks worldwide using a campaign called "ArcaneDoor" that exploits security flaws in Cisco ASA firewalls. Visa-related systems may have been compromised, according to reports.

The Sun newspaper reported that tens of thousands of files were stolen, though the government has not confirmed the scope of data accessed or number of affected individuals.

The Information Commissioner's Office, which mandates breach reporting within 74 hours, confirmed receiving notification about the incident and is reviewing the information provided.

The Foreign Office handles diplomatic communications, intelligence sharing and international security policy, making any compromise particularly concerning.