Chinese APT group likely using ransomware attacks as cover for IP theft

A China-based advanced persistent threat (APT) actor, active since early 2021, appears to be using ransomware and double-extortion attacks as camouflage for systematic, government-sponsored cyberespionage and intellectual property theft.

In all of the attacks, the threat actor has used a malware loader called the HUI Loader — associated exclusively with China-backed groups — to load Cobalt Strike Beacon and then deploy ransomware on compromised hosts. Researchers at Secureworks who are tracking the group as “Bronze Starlight” say it’s a tactic they have not observed other threat actors use.

Secureworks also says it has identified organizations in multiple countries that the adversary appears to have compromised. The group’s US-based victims include a pharmaceutical company, a law firm, and a media company with offices in Hong Kong and China. Others include electronic component designers and manufacturers in Japan and Lithuania, a pharmaceutical company in Brazil, and the aerospace and defense division of an Indian conglomerate. Some three-quarters of Bronze Starlight’s victims so far are organizations that have typically been of interest to government-sponsored Chinese cyber-espionage groups.

Cycling Through Ransomware Families

Since it began operations in 2021, Bronze Starlight has used at least five different ransomware tools in its attacks: LockFile, AtomSilo, Rook, Night Sky, and Pandora. Secureworks’ analysis shows that the threat actor used a traditional ransomware model with LockFile, where it encrypted data on a victim network and demanded a ransom for the decryption key. But it switched to a double-extortion model with each of the other ransomware families. In these attacks Bronze Starlight attempted to extort victims by both encrypting their sensitive data and threatening to leak it publicly. Secureworks identified data belonging to at least 21 companies posted on leak sites associated with AtomSilo, Rook, Night Sky, and Pandora.

While Bronze Starlight appears on the surface to be financially motivated, its real mission appears to be cyberespionage and intellectual property theft in support of Chinese economic objectives, says Marc Burnard, senior consultant information security research at Secureworks. The US government last year formally accused China of using threat groups such as Bronze Starlight in state-sponsored cyber-espionage campaigns.

“The victimology, tooling, and rapid cycling through ransomware families suggest that Bronze Starlight’s intent may not be financial gain,” he says. Instead, it’s possible that the threat actor is using ransomware and double extortion as a cover to steal data from organizations of interest to China and destroy evidence of its activity.

Bronze Starlight has consistently targeted only a small number of victims over short periods of time with each ransomware family — something that threat groups don’t often do because of the overhead associated with developing and deploying new ransomware tools. In Bronze Starlight’s case, the threat actor appears to have employed the tactic to prevent drawing too much attention from security researchers, Secureworks said.

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