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takyon writes:

Yes, of course there's now malware for Windows Subsystem for Linux

In 2017, more than a year after the introduction of WSL, Check Point researchers proposed a proof-of-concept attack called Bashware that used WSL to run malicious ELF and EXE payloads. Because WSL wasn't enabled by default and Windows 10 didn't ship with any preinstalled Linux distro, Bashware wasn't considered a particularly realistic threat at the time.

Four years later, WSL-based malware has arrived. The files function as loaders for a payload that's either embedded – possibly created using open-source tools like MSFVenom or Meterpreter – or fetched from a remote command-and-control server and is then inserted into a running process via Windows API calls.

"Threat actors always look for new attack surfaces," said Mike Benjamin, Lumen vice president of product security and head of Black Lotus Labs, in a statement. "While the use of WSL is generally limited to power users, those users often have escalated privileges in an organization. This creates blind spots as the industry continues to remove barriers between operating systems."

If there's a bright side to this anticipated development, it's that this initial WSL attack isn't particularly sophisticated, according to Black Lotus Labs. Nonetheless, the samples had a detection rate of one or zero in VirusTotal, indicating that the malicious ELFs would have been missed by most antivirus systems.

Original Submission