Cloud Threats Memo: Hard Times for ARM-based Mac M1 Processors

The Cloud Threats Memo is a weekly series from Paolo Passeri, digging into a recent cloud threat and highlighting how Netskope can best help mitigate it.

Just a few months after their debut in November 2020, the new ARM-based Mac M1 Processors have already attracted the unwanted attention of cybercriminals with two adware samples, the details of which have been revealed over the past few days.

First, security researcher Patrick Wardle discovered a variant of Pirrit, a Mac-targeting adware, compiled natively to run the new M1 architecture. Just a few days later, researchers at Red Canary have dissected another M1-compiled adware, dubbed Silver Sparrow (incidentally, my family name “Passeri” means “Sparrows” in English).

This second malware, Silver Sparrow, is particularly interesting, and not just because it has been compiled to run on the new M1 processor. Its command and control infrastructure is equally noteworthy since it is hosted on a well-known cloud service, AWS S3, where the malware checks in every hour to download a JSON file from an S3 bucket, which is then converted into a property list used to determine further actions. The Akamai CDN is also used in the process.

As of February 17th, Silver Sparrow had already spread its wings to reach 29,139 macOS endpoints in 153 countries (located primarily in the United States, the United Kingdom, Canada, France, and Germany), but its real intent is not clear. In more than a week of observation, the researchers haven’t seen a final payload delivered, leaving its ultimate goal a mystery. Nonetheless, according to the security researchers, the operation is the work of a mature adversary:

“AWS offers a highly available and resilient file distribution method. The adversary can create a bucket, serve out files, and operate without worrying about the additional network administration and overhead associated with doing all of this in-house. […]. This implies that the adversary likely understands cloud infrastructure and its benefits over a single server or non-resilient system. Further, the adversary that likely understands this hosting choice allows them to blend in with the normal overhead of cloud infrastructure traffic. Most organizations cannot afford to block access to resources in AWS and Akamai. The decision to use AWS infrastructure further supports our assessment that this is an operationally mature adversary.”

How Netskope mitigates this threat

The Netskope Next Gen Secure Web Gateway can apply granular controls to thousands of cloud services, blocking those activities that pose a risk for the organization, regardless of how they are executed (via a browser, a native client, or a script). In the case of AWS S3, the engine recognizes a number of different activities and allows organizations to differentiate policies based on the AWS instance or on S3 bucket constraints. 

Stay safe!