Justice minister David van Weel told MPs in a briefing that it appears the weakness had been used by third parties to access the department systems.

Tech expert Bert Hubert told BNR radio the breach poses a severe risk to national security. “This is not some back door that was left open – this is the front door. It does not get any scarier than this,” he said.

Hubert said it is still unclear whether any sensitive information was stolen, but stressed the extent of possible exposure is vast. “All the data employees can see goes through that system. You have to assume the hackers could see that too.”

OM systems are now largely unreachable and employees can no longer work remotely but no court cases have been delayed, officials said.

The National Cyber Security Centre (NCSC) had already issued warnings about the Citrix software in June and early July, urging organisations to take action.

The justice ministry said the department had applied Citrix’s recommended patches, but these failed to fully eliminate the flaw. It remains unclear how deeply hackers may have penetrated the network.