Cyber security officials have confirmed they are aiding an investigation after a minister said the UK government had been hacked.
Trade Minister Sir Chris Bryant said earlier that investigations were “ongoing” after an attack in October.
It is understood a Chinese affiliated group is suspected of being behind the attack.
The UK government has not named who it thinks is responsible, with a spokesperson saying it has been “working to investigate” the incident.
The UK’s National Cyber Security Centre (NCSC) said it is “working with government partners to fully understand the impact” after Home Office systems, operated by the Foreign Office, were accessed.
Speaking earlier on BBC Breakfast, Sir Chris said the security gap was “closed pretty quickly” and “we think that it is a fairly low-risk that individuals will have been compromised or affected”.
Speaking to Times Radio, he said: “I’m not able to say whether it is directly related to Chinese operatives, or indeed the Chinese state”.
The Sun newspaper has reported that the incident took place in October, with information possibly including visa details targeted.
The incident has been referred to the Information Commissioner’s Office.
UK intelligence agencies have warned about increasing, large-scale espionage from China, using cyber and other means, and targeting commercial and political information.
The cyber-agency GCHQ said last year that it was devoting more resources to counter threats from China than any other nation.
“Government facilities are always going to be potentially targeted,” Sir Chris said on Friday.
“We are working through the consequences of what this is.”
Confirmation of a hack by a Chinese state group would be awkward for the government ahead of a planned visit to Beijing next year by Sir Keir Starmer, the first by a UK prime minister since 2018.
The Labour government has said it is important to engage with China as it cannot be ignored on trade, climate change and other major issues, but face-to-face meetings also provide a forum for robust exchanges about issues affecting UK security.
The Chinese government has consistently denied it backs cyber-attacks targeting the UK.
Last year, responding to the UK government’s National Security Strategy, a spokesperson for the Chinese embassy in London said “accusations such as Chinese espionage, cyber-attacks, and transnational repression against the UK are entirely fabricated, malicious slander”.
Earlier this month, Sir Keir said UK government policy towards China could not continue to blow “hot and cold”.
Failing to navigate a relationship with China, he said, would be a “dereliction of duty” when China is a “defining force in technology, trade and global governance”.
Building a careful relationship would instead bolster the UK’s place as a leader on the international stage and help secure UK national interests, Sir Keir said, while still recognising the “reality” that China “poses national security threats”.
While it remains unclear how hackers gained access in this instance, Jamie MacColl, a senior research fellow in cyber and tech at the Royal United Services Institute (RUSI), told the BBC government departments often use “old IT” systems.
Jake Moore, global cybersecurity adviser to software company ESET, said government departments needed to invest in “better digital defences” because “they will continue to be targeted”.
