Belgium’s interior ministry has been victim of a cyberattack in which attackers gained access to the ministry’s entire computer system.

“The FPS Interior was the victim of a complex, sophisticated and targeted cyberattack. All necessary measures are taken,” the interior ministry said in a statement, adding that the attack bears signs of cyber-espionage.

The intrusion was discovered in March 2021 when technicians of the Center for Cybersecurity Belgium (CCB) launched an investigation after Microsoft disclosed four zero-day vulnerabilities in its Exchange email program that were targeted in attacks by China-linked hacker group Hafnium.

“It was during this investigation that the CCB's cyber-experts identified subtle tracks of questionable acts on the SPF network. The first tracks date from April 2019 and indicate a very sophisticated cyberattack. The complexity of this attack indicates an actor who has cyber capacities and extensive resources. The perpetrators acted in a targeted manner, which is reminiscent of espionage,” according to the statement.

The Federal Public Service Interior's communications director, Olivier Maerens, said that the ministry's servers were well protected and that the hackers had not gained access to the most sensitive data.

The FPS Interior did not share additional details regarding the hack citing ongoing investigation.

Earlier the month, Belgium's national public sector network Belnet was hit by a major DDoS (distributed denial of service) attack that crippled internet access for all institutions connected to the Belnet network, including the federal government and parliament, universities, researchers and reservations for the country's vaccination program.