An unnamed media organization in South Asia was targeted in November 20233 using a previously undocumented Go-based backdoor called GoGra.
“GoGra is written in Go and uses the Microsoft Graph API to interact with the control (C&C) server hosted by Microsoft Mail Services,” says Symantec, part of Broadcom. said in a report shared with The Hacker News.
It is currently unclear how this is delivered to target environments, GoGra is specifically configured to read messages on behalf of the Outlook user “FNU LNU” whose subject line begins with the word “Input”.
The message content is then decrypted using AES-256 in Cipher Block Concatenation (CBC) mode using the key, after which it executes commands via cmd.exe.
The results of the operation are then encrypted and sent to the same user with the subject “Output”.
GoGra is said to be the work of a nation-state hacking group known as Harvester due to its similarity to a custom .NET implant called Graphon that also uses the Graph API for C&C purposes.
The development comes at a time when threat actors are increasingly taking advantage of legitimate cloud services to remain discreet and avoid the need to purchase dedicated infrastructure.
Some of the other new malware families that used this method are listed below –
- A previously unseen data-stealing tool has been deployed Firefly as a result of a cyber attack targeting a military organization in Southeast Asia. Collected information is uploaded to Google Drive using a hard-coded refresh token.
- A new backdoor called Grager was deployed against three organizations in Taiwan, Hong Kong and Vietnam in April 2024. It uses the Graph API to communicate with the C&C server hosted on Microsoft OneDrive. The activity has been tentatively linked to a suspected Chinese threat actor who is being tracked UNC5330.
- The backdoor, known as MoonTag, contains functionality to communicate with the Graph API and is attributed to a Chinese-speaking threat actor
- A backdoor called Onedrivetools has been used against IT companies in the US and Europe. It uses the Graph API to interact with the C&C server hosted on OneDrive to execute received commands and save the output to OneDrive.
“Although the use of cloud services for command and control is not a new technique, recently more and more attackers have begun to use it,” Symantec said, pointing to malware such as BLUE WORLD, Graphite, Graphicand BirdyClient.
“The number of actors now deploying threats that use cloud services suggests that espionage actors are clearly studying threats created by other groups and imitating what they believe to be successful techniques.”
