The German drug manufacturer Bayer reported it was hit with a cyberattack launched from China that used WINNTI malware that resided on its network for at least one year.

The company told Reuters it found the malware in its system in early 2018 and then studied and analyzed until last month when it was removed. A Bayer spokesman told Reuters there is no evidence of data was removed, but the company is still studying the overall impact the malware had on its system.

The company is not exactly sure when the malware was injected.

Bayer’s internal cybersecurity team said the attackers used WINNTI malware, a trojan associated with a Chinese APT group of the same name.