You don’t need to say the words “sandboxed” or “isolated” to say effectively the same thing. Your goal with distrobox was to keep the AUR malware separate from your normal system, no?
Security through obscurity is not security. The malware can do the same data exfiltration regardless of root access because the AUR malware has been about stealing secrets in user-readable directories. Setting a custom home for distrobox does not disallow access to the normal one.
Say for example that your default user home is /home/user and you set the distrobox home to /tmp/home
If you run ls $HOME inside distrobox it will list files in /tmp/home, but just as easily you could run ls /home/$USER and it would list in your default home. Or alternatively just use the find command and steal secrets without targeting the user home.
This is because changing the user home through distrobox doesn’t do anything about preventing directory traversal to your default home.
If your goal is to create a different environment and you don’t care that it won’t stop malware, use Incus or Podman directly. Distrobox is the wrong choice.
My point was simple: when dealing with malware, distrobox is not an effective method of creating a “different environment” because that is antithetical to its stated goals.
You can do whatever you want, I am not here to police your choice on your personal system. I only take issue with recommending this strategy to others.
Things sandboxed by Firejail share the same host kernel. Therefore, kernel vulnerabilities could allow for privilege escalation.
Firejail itself is a security-hole. It is a massive root SetUID binary which can and has been used for privilege escalation. I avoid it entirely. Unprivileged sandboxes are better, but lack the built-in profiles provided by Firejail.
If I was trying to sandbox malware, I would use sydbox. It is memory safe (unlike Firejail or Bubblewrap), unprivileged (unlike Firejail), secure sandbox by default (unlike Bubblewrap), extensively uses all relevant Linux security features/modules (more than any other), and actually helps to stop LPE by re-implementing or denying dangerous syscalls like in the case of many of the recent vulnerabilities. Biggest caveat is that it’s not for beginners, even though it abstracts a lot of the complexity. I’d also neverbrun malware in just a sandbox, but use that alongside a proper VM.
TL;DR No sandbox will save you from good malware. Firejail might be enough for script kiddies, but could make your system more vulnerable to privilege escalation attacks. Avoid installing things you don’t need.