TrickBot’s stealthy BazarBackdoor malware written in Nim programming language. TrickBot cybercrime gang has been increasingly distributing their newer and stealthier malware. Nim takes its inspiration from Python, Ada, and Modula and can generate executables supported on Windows, macOS, and Linux. The crime group likely chose to pursue the lightweight malware development in Nim to frustrate anti-virus and detection mechanism focused on traditional binaries compiled in C/C++ style languages. Other malware developed in Nim is a ransomware family called XCry [VirusTotal] discovered by MalwareHunterTeam.
Source: https://www.bleepingcomputer.com/news/security/trickbots-bazarbackdoor-malware-is-now-coded-in-nim-to-evade-antivirus/