Threat Signal Report

New MacOS Malware Variant - "Silver Sparrow" Affecting Over 30,000 MacOs Machines WorldWide

Description

FortiGuard Labs is aware of a newly discovered MacOS malware variant affecting over 30,000 computers in a global campaign. The malware dubbed "Silver Sparrow" was discovered by researchers at Red Canary. Classified as a downloader, what makes this MacOS variant unique is that there is no observed activity of a malicious payload being downloaded to victim machines. Another interesting observation is that the downloader has the capability to support the new Apple M1 ARM64 architecture which was recently released in late 2020, adding more intrigue about the malware itself and the threat actors behind it.


What are the Technical Details of the Threat?

Observations of the Silver Sparrow binaries highlight two different compiled binaries, one that is compiled for the Intel x86_64 architecture and another for the Intel x86_64 and M1 ARM64 architectures. Both files have similar names (update.pkg and updater.pkg) and both use a novel JavaScript execution routine. Further analysis is complicated because the routine uses a legitimate Mac installer process that does little to provide insight into the JavaScript commands being used by the installation package. To establish persistence, the malware uses plistbuddy, a built in tool to create property lists, including LaunchAgents. Finally, the LaunchAgent uses a process to execute a shell script that downloads a JSON file from a C2 server for further instructions.


What Operating Systems are Affected?

Mac Operating Systems.


How Serious of an Issue is This?

HIGH. This is due to the high installation rates and spread of the malware.


What is the Status of Coverage?

FortiGuard Labs has the following AV coverage in place for known Silver Sparrow samples as:


OSX/Agent.BL!tr


For FortiEDR protections, all published IOC's were added to our Cloud intelligence and will be blocked if executed on customer systems.


All Network IOC's related to this threat are blocked by the FortiGuard WebFiltering Client.


Any Other Suggested Mitigation?

Due to the ease of disruption and potential for damage to daily operations, reputation, and unwanted release of personally identifiable information (PII), etc., it is important to keep all AV and IPS signatures up to date. It is also important to ensure that all known vendor vulnerabilities within an organization are addressed, and updated to protect against attackers establishing a foothold within a network.


Also - organizations are encouraged to conduct ongoing training sessions to educate and inform personnel about the latest phishing/spearphishing attacks. They also need to encourage employees to never open attachments from someone they don't know, and to always treat emails from unrecognized/untrusted senders with caution. Since it has been reported that various phishing and spearphishing attacks have been delivered via social engineering distribution mechanisms, it is crucial that end users within an organization be made aware of the various types of attacks being delivered. This can be accomplished through regular training sessions and impromptu tests using predetermined templates by an organizations' internal security department. Simple user awareness training on how to spot emails with malicious attachments or links could also help prevent initial access into the network.


Definitions

Traffic Light Protocol

Color When Should it Be used? How may it be shared?

TLP: RED

Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.

TLP: AMBER

Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.

TLP: GREEN

Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.

TLP: WHITE

Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.