U.S. and Japanese security agencies have issued a warning over China-backed cyberattacks that exploited routers in order to gain access to corporate headquarter networks in the two countries.

BlackTech, a Chinese government-linked group that has been active since 2010, has targeted a variety of sectors including government, technology and telecommunications, as well as military-linked entities, the agencies said Wednesday. The group also breached company headquarters through the infiltration of international subsidiaries.

The group has deployed a range of tactics in order to breach security — from customized malware and compromising routers to the “living off the land” technique, which describes hackers’ exploitation of legitimate software as an entry point and then parasitically blending into the background.