The Ministry of Defence has been targeted in a massive data breach, it is understood.
Service personnel and veterans are thought to have been targeted in the hack, with names and bank details potentially compromised.
Sky News reported that China is believed to be behind the breach.
The system which was targeted is not connected to the main MoD computer systems, and has been taken down and a review of the system launched.
The attack comes as the government has increased warnings about cyber threats from ‘hostile states and third parties’.
It is understood that initial investigations have found no evidence that data has been removed.
No issues are expected when employees are next paid, and there was no impact on salaries at the most recent payday.
Defence Secretary Grant Shapps is expected to make a Commons statement tomorrow afternoon, when parliament returns from the Bank Holiday.
However, ministers will not name the country responsibly for the hacking, and will blame hostile and malign actors.
Service personnel who have been affected by the breach will be alerted as a precaution and provided with specialist advice.
Staff at the MoD have been making efforts to work out the scale of the attack since it was discovered several days ago.
Labour’s shadow defence secretary John Healey said: ‘So many serious questions for the defence secretary on this, especially from Forces personnel whose details were targeted.
‘Any such hostile action is utterly unacceptable. Parliament will expect a full Commons statement tomorrow.’
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