Knock, Knock – Who’s There?

Following our research from Evil Twins and Windows Linux Subsystem, interoperability between different WSL versions was something that caught our attention. The protocol and mechanism to do file management from/to WSL is a must for Blue and Red Teams whose research will provide new ways to execute known techniques to achieve tactics such as Persistence, Defense Evasion and Execution, among others.

It is important (even if not seen today in regular arsenals) to understand how to protect, detect and react to this attack surface which could be widely spread in the future where WSL could be a de-facto component in every Enterprise machine.

Since Windows 10 version 1903, it is possible to access Linux files from Windows by using the \wsl$[DistroName] path syntax using 9P protocol. During our research, we found some design issues in WSLv1 that were propagated to WSLv2 — even though the core component differs.

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Source: McAfee