GraphSteel and GrimPlant Backdoors have been used in conducting cyberattacks on Ukrainian authorities. The backdoors allow threat actors to gain unauthorized access and control of the victim’s system. Government agencies in Ukraine received emails with the topic “Wage arrears” or “Заборгованість по зарплаті” with an excel file of the same name. While the file does contain legitimate statistics, it is also contains hex-coded data and macros. Once the macro is executed, it will decode the data, create a new executable file “Base-Update.exe” on the computer and execute it.
This file is a downloader developed using the GoLang programming language. The program will download and run another bootloader, which, in turn, will download and run malware GraphSteel and GrimPlant on your computer. – CERT-UA
These attacks have been attributed to UAC-0056 aka UNC2589, TA471, or SaintBear.