A state-backed Chinese hacking group called APT41 were able to hack into telecommunications firms' servers and steal the contents of text messages for intelligence that was of interest to Beijing, according to a new report from cybersecurity firm FireEye.

State-backed Chinese hackers were able to hack into telecommunications firms and steal the contents of text messages of "geopolitical interest" to Beijing, according to a new report.

The group, known as APT41, used a malicious piece of software or malware dubbed "Messagetap" to access servers responsible for sending and storing text messages, cybersecurity firm FireEye said. The company did not disclose the name of the telecom company.

Once in, the malware would search the contents of text messages for keywords of "geopolitical interest to Chinese intelligence collection." It would also search for specific phone numbers of certain people from a database that the hackers had and were targeting.

While FireEye did not disclose which countries or individuals were targeted, the revelation of the hacking campaign comes at a time of increased concern about China's use of technology for espionage. The U.S. has accused telecommunications equipment maker Huawei of being a national security threat and suggested that its gear could be used for espionage purposes by Beijing. Huawei has repeatedly denied these allegations.