Backdoor for Windows, macOS, and Linux went undetected until now
Researchers have uncovered a never-before-seen backdoor written from scratch for systems running Windows, macOS, or Linux that remained undetected by virtually all malware scanning engines.
Researchers from security firm Intezer said they discovered SysJoker—the name they gave the backdoor—on the Linux-based Webserver of a “leading educational institution.” As the researchers dug in, they found SysJoker versions for both Windows and macOS as well. They suspect the cross-platform malware was unleashed in the second half of last year.
The discovery is significant for several reasons. First, fully cross-platform malware is something of a rarity, with most malicious software being written for a specific operating system. The backdoor was also written from scratch and made use of four separate command-and-control servers, an indication that the people who developed and used it were part of an advanced threat actor that invested significant resources. It’s also unusual for previously unseen Linux malware to be found in a real-world attack.
Analyses of the Windows version (by Intezer) and the version for Macs (by researcher Patrick Wardle) found that SysJoker provides advanced backdoor capabilities. Executable files for both the Windows and macOS versions had the suffix .ts. Intezer said that may be an indication the file masqueraded as a type script app spread after being sneaked into the npm JavaScript repository. Intezer went on to say that SysJoker masquerades as a system update.
