Are there any security hazards to installing Ubutnu for Windows 10?

Question

I only want a bash shell in Windows 10 that runs faster and doesn't have any of the quirks of git bash / MINGW64, like for instance all of that CRLF garbage.

Is there any security harm in installing it? I mean I'm sure depending on what you install with apt-get there could be issues, but what if you're just installing Ubuntu for Windows 10 and git?

I noticed that I could not run iptables -L I got some error:

iptables v1.6.1: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

Answer 1

Any new piece of software potentially increases attack surface. However I think that Ubuntu on WSL does not open any massive holes as-is. WSL works by mapping Linux syscalls onto Windows equivalencies. So it cannot do anything that any Windows program could not do. It does not listen on sockets and terminates when you close it - it cannot run daemons. The risk comes if you install or run untrusted code, or an upstream is compromised. Unless you do something egregious like configuring any downloaded .sh to run in WSL or something you are not exposed to any extra risk that would not be running Ubuntu natively.

So you do have more ways to shoot yourself in the foot, but that’s all. Exactly the same as if you ran WINE on Linux.

Answer 2

Including a subsystem on a windows machine can be "ok", but then you have to secure two systems instead of just one. Since it is not fully compatible with Windows (as far i know, it's just another one). It can allow a malicious actress to use the subsystem as a way to hide possible malware also called Bashware (https://research.checkpoint.com/beware-bashware-new-method-malware-bypass-security-solutions/).

Answer 3

"Running Sensitive Apps in WSL: (SAFE + SAFE) < SAFE" presents several significant security issues that are fundamentally a part of WSL:

• WSL is a Windows utility that allows users to run Linux applications under Windows.
• Any standard (non-admin) Windows process has full access rights to all the files that make up the WSL machine.
• If a malicious program runs as this standard process, it can steal sensitive static data (e.g., SSH keys) by simply copying them from the WSL file system.
• By modifying the programs in the WSL file system, our malicious program can also capture sensitive dynamic data (e.g., usernames, passwords, passphrases).
• The WSL design allows the activation of Windows processes by programs running inside the Linux machine. Therefore, a standard (non-root) Linux program can completely take over the Linux machine.
• WSL 2, designed as a “lightweight Utility VM”, has markedly diminished the attack surfaces of WSL, but is still vulnerable to the security weakness described here.
• Bottom line: Running sensitive applications inside WSL is significantly less secure than running the equivalent applications in a standalone Windows or Linux Desktop system.

Also, as of October 2020, WSL 2 bypasses Windows Firewall, so you would have to make sure to have the same firewall rules in Linux itself as well as in Windows.

(Copied from my answer to Should a windows IT shop have concerns about enabling WSL for users?)