Cloud Threats Memo: Scary Examples of Weaponizing Google Drive

The abuse of Google Drive to deliver malicious content continues, and two recent examples remind us how the flexibility of this cloud storage tool can be easily weaponized by malicious actors. And the spectrum of content that can be distributed, and victims that can be targeted is surprising.

In the first example, attributed to a group of hackers recruited in a Russian-speaking forum, the Google Threat Analysis Group has dismantled a financially motivated phishing campaign targeting YouTubers with Cookie Theft malware, a session hijacking technique that enables access to user accounts with session cookies stored in the browser. The purpose of this campaign, luring the victims with fake collaboration opportunities, was to hijack their YouTube channel and then either sell it or use it for cryptocurrency scams.

The phishing typically started with a customized email introducing a company and its products (1,011 domains, some of them impersonating legitimate companies), and once the target agreed to the deal, a malware landing page disguised as a software download URL was sent via email or a PDF on Google Drive, and in a few cases, Google Documents containing the phishing links. To give you an idea of how easily these services can be exploited for large-scale campaigns, Google identified around 15,000 accounts, some of which were explicitly created for this campaign.

An additional (literally) scary campaign spotted by Cofense has delivered the MirCop ransomware via an articulated multi-stage kill chain where once again Google Drive plays an important (initial) role. This specific attack started via a business-related email, suggesting a previous agreement between the sender and the victim, and containing the link to a supposed “DWG following Supplies List” hosted on a Google Drive URL. Besides evading Secure Email Gateways, Google Drive provides legitimacy to the email and in the user’s mind is also associated with a service used to exchange business communications. The linked document is an MHT file (a web archive file type) that, once executed, downloads a RAR compressed file. The RAR archive itself contains an executable, a DotNET loader that uses VBS scripts to drop and run the MIRCOP ransomware. And yes, this infection is scary since, among other things, the ransomware changes the home screen to a gory image.

These two examples demonstrate how simply Google Drive can be weaponized for large-scale campaigns in multiple ways. And these examples are not the only ones: a simple search on URLhaus is worth more than a thousand words (do you recognize two old acquaintances such as BazarLoader and GuLoader?)

How Netskope mitigates the risk of rogue cloud instances abused to deliver malicious content

There are multiple stages of the attack chain where the Netskope Next-Gen SWG can mitigate this threat.

• It is possible to block the access (and in general enforce granular controls) to dozens of non-corporate cloud services such as Google Drive (including personal instances of corporate services or non-corporate instances abused by the attackers).
• Downloading a malicious document from a web page or a cloud service can be prevented by the Threat Protection Engine that offers multiple engines including signature-based AV, advanced heuristics, sandboxing, and a ML-based scanner for malicious documents and executables.
• Any redirection within the kill chain can be prevented by the content filtering engine that offers 16 granular security risk categories, including phishing and malware distribution points.
• The Cloud Threat Exchange, a component of Netskope Cloud Exchange improves attack neutralization via bi-directional automated IoC sharing (hashes, IPs, domains, and URLs) with third-parties such as EDR technologies and threat intelligence feeds.
• Netskope Advanced Analytics provides a specific Threat Protection Dashboard with rich insights on malicious traffic to non-corporate cloud instances and web pages, most targeted users, top applications exploited to deliver malicious content, etc. A valuable tool for SOC teams and Incident responders.

Stay safe!