A newly uncovered APT is relying on legitimate services for command-and-control (C&C) communication and data exfiltration, ESET warns.
Tracked as GopherWhisper (PDF) and active since at least November 2023, the hacking group is operating out of China, as timestamp inspection of chat messages and emails has revealed.
The APT came to the spotlight in January 2025, during the investigation into a Go-based backdoor found on the systems of a governmental entity in Mongolia, which led to the identification of several other backdoors, custom loaders, and injectors associated with the group.
Dubbed LaxGopher, the backdoor uses Slack for C&C communication and can execute commands via command prompt, exfiltrate victim data, and fetch and execute additional payloads on the infected machines. GopherWhisper, ESET says, mainly used LaxGopher to enumerate drives and files.
An injector named JabGopher is used to execute the backdoor in the memory of a newly spawned instance of svchost.exe.
One of the tools that LaxGopher can deploy is CompactGopher, a file collector written in Go that can compress files from the command line and send them to the file.io file-sharing service using a public REST API.
Another tool in GopherWhisper’s arsenal is RatGopher, a Go-based backdoor. Unlike LaxGopher, it uses Discord for C&C communication. It can open new instances of the command prompt and upload or download files from file.io.
The APT also relies on a C++ backdoor called SSLORDoor, which uses OpenSSL BIO for communication via raw TCP sockets. The malware can spawn a hidden command prompt process, enumerate drives, execute commands related to file manipulation, and create new socket connections.
ESET’s investigation uncovered two additional tools that GopherWhisper deployed against the same Mongolian government organization, namely the BoxOfFriends Go backdoor that relies on the Microsoft Graph API for communication via draft Outlook messages, and the FriendDelivery DLL injector that loads it.
The BoxOfFriends backdoor can exfiltrate files, manipulate ports, and execute supplied commands through a shell opened on the host.
The China-linked APT infected roughly 12 systems within the victim Mongolian governmental institution. According to ESET, dozens of other victims were likely targeted as well.
“Due to the lack of similarities in code, TTPs, and targeting to any existing APT group, we have created GopherWhisper as a new group and attribute the described toolset to it,” ESET notes.
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