ANOTHER BRICKSTORM: STEALTHY BACKDOOR ENABLING ESPIONAGE INTO TECH AND LEGAL SECTORS

Summary from the TLDR InfoSec newsletter

China-nexus threat actor UNC5221 uses BRICKSTORM backdoors on network appliances and VMware infrastructure to maintain persistent access, averaging 393 days undetected. The actor employs sophisticated tactics, including VM cloning to extract credentials offline, credential harvesting via BRICKSTEAL servlet filters, and legitimate tool abuse to access M365 mailboxes and secret vaults. Organizations should inventory unmonitored appliances, hunt for unusual internet traffic from management interfaces, and monitor for VM cloning activities and suspicious SSH enablement on virtualization platforms.