The American multinational software company Microsoft warned that hackers supported by the Chinese government gained access to email accounts of its Exchange Server service for companies.
In a post on the company's official blog, its corporate vice president for security and user trust, Tom Burt, said the hackers took advantage of four previously unknown system weaknesses.
This group of Chinese government-backed hackers sought to steal information from US organizations in fields as diverse as infectious disease research, law firms, higher education, defense contractors, think tanks, and NGOs.
Through the flaws in the system that the hackers were able to identify, they gained access to the server, from which they were able to steal information such as email accounts and contacts and at the same time install elements of malicious software or malware.
Last December, the company specializing in cybersecurity FireEye, one of the largest in the US, reported that hackers linked to the government of a foreign country - suspicions center on Russia - managed to access their systems and steal material.
On that occasion, FireEye described the attacker as "highly sophisticated" and made available to its clients a series of tools designed to counteract any attack in the event that hackers try to use the stolen material to access their equipment.
The material stolen by the hackers in that case were products that the firm uses to detect weaknesses in its clients' networks and thus remedy them, so they could be used for precisely the opposite: identify vulnerabilities and proceed to attack.