China-linked threat actors compromised some U.S. internet service providers as part of a cyber espionage campaign code-named Salt Typhoon.

The state-sponsored hackers aimed at gathering intelligence from the targets or carrying out disruptive cyberattacks.

The Wall Street Journal reported that experts are investigating into the security breached to determine if the attackers gained access to Cisco Systems routers, which are core network components of the ISP infrastructures.

A threat activity cluster tracked as Earth Freybug has been observed using a new malware called UNAPIMON to fly under the radar.

"Earth Freybug is a cyberthreat group that has been active since at least 2012 that focuses on espionage and financially motivated activities," Trend Micro security researcher Christopher So said in a report published today.