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posted by requerdanos on Monday September 20 2021, @02:15AM   Printer-friendly
from the Linux-security-Microsoft-style dept.

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.


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  • (Score: 2, Interesting) by Anonymous Coward on Monday September 20 2021, @03:08AM (1 child)

    by Anonymous Coward on Monday September 20 2021, @03:08AM (#1179577)

    The former implemented Linux on top of Windows system calls.

    The latter implements a VM using Hyper-V.

    I can imagine WSL 1 escaping a sandbox but WSL 2 should be a different kettle of fish re paravirtualization.

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  • (Score: 4, Informative) by TheRaven on Monday September 20 2021, @08:48AM

    by TheRaven (270) on Monday September 20 2021, @08:48AM (#1179620) Journal
    Yes and no. You might not be able to directly attack the NT kernel from WSL2 but you have a couple of solid attack vectors. First, /mnt/c is a 9p-over-VMBus mount of C:, so you have full FS access with the permissions of the user that invoked WSL2. Second, there's a binfmt image activator that passes the path and arguments to NT and runs PE/COFF binaries on the host kernel. This means that you can run arbitrary code on the host (again, with the permissions of the user that invoked WSL2). You also have quite a rich attack surface over VMBus against the host kernel.
    --
    sudo mod me up