Chinese hackers have used a flaw in a popular email security device to break into the networks of hundreds of public and private sector organizations around the world, Mandiant, a company specializing in cybersecurity, revealed on Thursday.

"This is the largest known cyber espionage campaign with links to China since the mass exploitation of Microsoft Exchange in early 2021," said Mandiant's technology manager, Charles Carmakal, in a statement quoted by Notícias ao Minuto.

Google-owned technology company Mandiant has admitted with "high certainty" that the group that exploited the software vulnerability in Barracuda Networks' email Security Gateway was involved in "espionage activities on behalf of the People's Republic of China".

In the released statement, Mandiant further revealed that the spying activity began in October last year.

The hackers sent emails containing malicious file attachments in order to gain access to the devices and data of the targeted organizations, he said.

Also according to Notícias ao Minuto, among the organizations targeted, 55% were from North, Central and South America, 22% from Asia-Pacific and 24% from Europe, the Middle East and Africa and included foreign ministries in Southeast Asia, foreign trade departments and universities and academic institutions in Taiwan and Hong Kong.

The source also says that on June 6 this year, US company Barracuda claimed that some of its email security devices had been hacked in October last year, giving intruders access to the compromised networks.

The action was so serious that the US company, located in the state of California, recommended that the devices be completely replaced.