A previously unseen actor, likely nation-state-backed, is targeting organizations in South Asia, with a focus on Afghanistan, in what appears to be an information-stealing campaign using a new toolset.
The Harvester group uses both custom malware and publicly available tools in its attacks, which began in June 2021, with the most recent activity seen in October 2021. Sectors targeted include telecommunications, government, and information technology (IT). The capabilities of the tools, their custom development, and the victims targeted, all suggest that Harvester is a nation-state-backed actor.
New toolset deployed
The most notable thing about this campaign is the previously unseen toolset deployed by the attackers.
The attackers deployed a custom backdoor called Backdoor.Graphon on victim machines alongside other downloaders and screenshot tools that provided the attackers with remote access and allowed them to spy on user activities and exfiltrate information.
We do not know the initial infection vector that Harvester used to compromise victim networks, but the first evidence we found of Harvester activity on victim machines was a malicious URL. The group then started to deploy various tools, including its custom Graphon backdoor, to gain remote access to the network. The group also tried to blend its activity in with legitimate network traffic by leveraging legitimate CloudFront and Microsoft infrastructure for its command and control (C&C) activity.
- Backdoor.Graphon - custom backdoor that uses Microsoft infrastructure for its C&C activity
- Custom Downloader - uses Microsoft infrastructure for its C&C activity
- Custom Screenshotter - periodically logs screenshots to a file
- Cobalt Strike Beacon - uses CloudFront infrastructure for its C&C activity (Cobalt Strike is an off-the-shelf tool that can be used to execute commands, inject other processes, elevate current processes, or impersonate other processes, and upload and download files)
- Metasploit - an off-the-shelf modular framework that can be used for a variety of malicious purposes on victim machines, including privilege escalation, screen capture, to set up a persistent backdoor, and more.
The custom downloader used by the attackers leverages the Costura Assembly Loader. Once on a victim machine, it checks if the following file exists:
If the file does not exist it downloads a copy from the following URL:
Next, the sample creates the following file if it does not exist:
- "[ARTEFACTS_FOLDER]\Microsoft Services[.]vbs"
Then it sets the following registry value to create a loadpoint:
- HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\"MicrosoftSystemServices" = "[ARTEFACTS_FOLDER]\Microsoft Services[.]vbs"
Finally it opens an embedded web browser within its own UI using the following URL:
While it initially appeared that this URL may have been a loadpoint for Backdoor.Graphon, upon further investigation it appears to be a decoy to confuse any affected users.
Backdoor.Graphon is compiled as a .NET PE DLL with export “Main” and the following PDB file name:
- D:\OfficeProjects\Updated Working Due to Submission\4.5\Outlook_4.5\Outlook 4.5.2 32 bit New without presistancy\NPServices\bin\x86\Debug\NPServices[.]pdb
When this is executed, it attempts to communicate with the attackers’ C&C servers, which are hosted on Microsoft infrastructure.
The attackers then run commands to control their input stream and capture the output and error streams. They also periodically send GET requests to the C&C server, with the content of any returned messages extracted and then deleted.
Data that cmd.exe pulled from the output and error streams is encrypted and sent back to the attackers’ servers.
The custom screenshot tool was also packed with the Costura Assembly Loader. The screenshot tool takes photos that it saves to a password-protected ZIP archive for exfiltration, with all archives older than a week deleted.
While we do not have enough evidence yet to attribute Harvester’s activity to a specific nation state, the group’s use of custom backdoors, the extensive steps taken to hide its malicious activity, and its targeting all point to it being a state-sponsored actor. Harvester’s use of legitimate infrastructure to host its C&C servers in order to blend in with normal network traffic is one example of the stealthy steps taken by this actor.
The targeting of organizations in Afghanistan in this campaign is also interesting given the huge upheaval seen in that country recently. The activity carried out by Harvester makes it clear the purpose of this campaign is espionage, which is the typical motivation behind nation-state-backed activity.
That Harvester’s most recent activity was seen earlier this month means that organizations in the sectors and geographies mentioned should be alert to the malicious activity outlined in this blog.
For the latest protection updates, please visit the Symantec Protection Bulletin.
Indicators of Compromise
hxxps://perfect-couple.com/perfectcouple[.]exe – sample was downloaded from this address
BLOG UPDATED 2.45pm, October 18, 2021: Minor updates made for clarity
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