Cloud Threats Memo: Cyber Espionage Exploiting Google Drive for C2 Infrastructure

Another day, another legitimate cloud service exploited for a cyber espionage campaign…

Researchers at ESET recently discovered Dolphin, a previously unreported backdoor used by the North-Korean threat actor APT37 (AKA ScarCruft and Reaper) against selected targets. The backdoor, deployed after the initial compromise using less sophisticated malware, was observed for the first time in early 2021, during a watering-hole attack on a South Korean online newspaper. Since then, the threat actors have continued to release new enhanced versions aimed to add more capabilities and make the backdoor even more evasive.

Dolphin has multiple features, including the ability to monitor drives and portable devices, exfiltrate files of interest, capture keystrokes, take screenshots, and steal credentials from browsers. Interestingly, in what appears as the latest example of a cloud service exploited in a cyber espionage campaign, Dolphin abuses Google Drive for its command and control (C2) communication.

APT37 is not the first example of an advanced persistent threat exploiting a legitimate cloud service as the command and control infrastructure or to exfiltrate the stolen data. And even if other services, like Dropbox, are abused more frequently by cyber espionage groups, this operation confirms  state-sponsored threat actors’ growing interest towards cloud services to make their attacks more evasive, with new apps constantly joining the unwelcome list of those exploited in cyber espionage campaigns.

How Netskope mitigates the risk of a legitimate cloud service exploited to host C2 infrastructure

Google Drive (like Dropbox) is one of thousands of services where the Netskope Next Gen SWG can provide granular access control and one of the dozens for which instance detection is also available. In similar cases where Google Drive is abused for command and control communication, it is possible to configure a policy that blocks access or potentially dangerous activities (such as upload and download) to non-corporate instances. It is also possible to make the scope of the policy broader, creating a policy on a category basis for any activities on unneeded cloud storage service that can potentially be exploited for command and control communication or malware delivery.

Malware delivery from a cloud storage service can be prevented through Netskope Threat Protection, part of the NG-SWG, which provides an effective defense against modern evasive threats regardless of the nature of the traffic (web or cloud) with a layered approach that offers multiple engines, ranging from antivirus to cloud sandboxing, plus additional detectors based on machine learning to detect Office documents containing malicious macros and portable executables.

Finally, Netskope Advanced Analytics provides complete visibility through multiple dashboards (including a dedicated one for the threat protection component) that provide rich insights and visibility into the traffic to non-corporate cloud instances: a valuable tool for SOC teams and incident responders.

Stay safe!