Chinese hackers have breached Belgium's State Security Service (VSSE), stealing 10% of emails between 2021 and May 2023.Investigators are looking into the security breach by China-linked threat actors on the VSSE.The hackers exploited a vulnerability in the Barracuda Email Security Gateway Appliance used by VSSE and others.10% of the VSSE's incoming and outgoing emails were compromised, exposing personal data of staff and applicants.No classified information was affected, and no stolen data has been found on the dark web.The Chinese embassy in Belgium has not yet commented on the accusation.Mandiant researchers linked China-linked threat actors to similar attacks exploiting the Barracuda ESG zero-day vulnerability globally.Barracuda warned customers of the zero-day flaw (CVE-2023-2868) exploited in May and provided patches.The flaw was exploited to deploy malware providing persistent backdoor access.The attackers used malware families like SALTWATER, SEASPY, and SEASIDE to exploit the vulnerability.