State-Backed HazyBeacon Malware Uses AWS Lambda to Steal Data from SE Asian Governments

Governmental organizations in Southeast Asia are the target of a new campaign that aims to collect sensitive information by means of a previously undocumented Windows backdoor dubbed HazyBeacon.

The activity is being tracked by Palo Alto Networks Unit 42 under the moniker CL-STA-1020, where “CL” stands for “cluster” and “STA” refers to “state-backed motivation.”

“The threat actors behind this cluster of activity have been collecting sensitive information from government agencies, including information about recent tariffs and trade disputes,” security researcher Lior Rochberger said in a Monday analysis.

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The exact initial access vector used to deliver the malware is currently not known, although evidence shows the use of DLL side-loading techniques to deploy it on compromised hosts. Specifically, it involves planting a malicious version of a DLL called “mscorsvc.dll” along with the legitimate Windows executable, “mscorsvw.exe.”

Once the binary is launched, the DLL proceeds to establish communication with an attacker-controlled URL that allows it to execute arbitrary commands and download additional payloads. Persistence is achieved by means of a service that ensures the DLL is launched even after a reboot of the system.

HazyBeacon is notable for the fact that it leverages Amazon Web Services (AWS) Lambda URLs for command-and-control (C2) purposes, demonstrating threat actors’ continued abuse of legitimate services to fly under the radar and escape detection.

“AWS Lambda URLs are a feature of AWS Lambda that allows users to invoke serverless functions directly over HTTPS,” Rochberger explained. “This technique uses legitimate cloud functionality to hide in plain sight, creating a reliable, scalable and difficult-to-detect communication channel.”

Downloaded among the payloads is a file collector module that’s responsible for harvesting files matching a specific set of extensions (e.g., doc, docx, xls, xlsx, and pdf) and within a time range. This includes attempts to search for files related to the recent tariff measures imposed by the United States.

The threat actor has also been found to employ other services like Google Drive and Dropbox as exfiltration channels so as to blend in with normal network traffic and transmit the gathered data. In the incident analyzed by Unit 42, attempts to upload the files to the cloud storage services are said to have been blocked.

In the final stage, the attackers run cleanup commands to avoid leaving traces of their activity, deleting all the archives of staged files and other payloads downloaded during the attack.

“The threat actors used HazyBeacon as the main tool for maintaining a foothold and collecting sensitive information from the affected governmental entities,” Rochberger said. “This campaign highlights how attackers continue to find new ways to abuse legitimate, trusted cloud services.”

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