FakeNet not out of the box in REMnux

[emtuls]

What's the problem?

While not directly FlareVM related, we do make a custom script to assist with modifying REMnux a little bit with our own small mods via our build script and config.

With this, we can make a crucial adjustment to FakeNet to make it work out of the box when REMnux is used as a standalone Linux Malware analysis environment.

Currently, FakeNet sets its NetworkMode to Auto, which defaults to MultiHost on Linux. This is an issue for a standalone analysis VM and causes FakeNet to not work at all with an error of Cannot fix gateway, as MultiHost is intended to be for when there are multiple VMs connected, not for a single VM being used on its own.

With REMnux being primarily used as a standalone Linux Malware Analysis environment for us, it makes more sense for FakeNet to default to SingleHost mode, which allows everything to work as intended on Linux.

I propose we make a small adjustment to the default.ini (located at /opt/fakenet-ng/lib/python3.8/site-packages/fakenet/configs/default.ini ) in REMnux to force SingleHost for NetworkMode.

Steps to Reproduce

1. Start REMnux
2. Try using FakeNet (sudo fakenet)
3. Note that pings, curls, and browsing to websites does not work as intended with FakeNet.

Environment

REMnux

Additional Information

No response

[Suresh-Krishna-P]

Hello @emtuls,

I’d like to work on this issue and have outlined a proposed implementation strategy below. I’d appreciate your feedback.

Implementation Plan

1. Configuration File Modification

• File: [remnux.yaml]
• Action: Add a new command block in the CMDS section
• Purpose: Execute a configuration command during REMnux build to modify FakeNet's default settings

2. Configuration Command

• Target file: /opt/fakenet-ng/lib/python3.*/site-packages/fakenet/configs/default.ini
• Change: Modify NetworkMode from Auto to SingleHost
• Method: Use sed to replace the configuration parameter

3. Placement Strategy

• Insert after the existing DNS/systemd-resolved fix (around line 29)
• Before IDA installation commands
• This ensures FakeNet is properly configured early in the build process

4. Build Integration

• Leverage existing build infrastructure: [vbox-build-remnux.py]
• No changes needed to build scripts—just YAML configuration
• Command executes automatically during standard VM build

Files to Modify

• [remnux.yaml](single file change)

Verification Method

• Build test REMnux VM with modified config
• Verify FakeNet NetworkMode setting in built VM
• Test FakeNet functionality: pings, curl, web browsing

Expected Outcome

REMnux VMs built with this configuration will have FakeNet properly configured for standalone operation, eliminating the "Cannot fix gateway" error on first use.

If you’re okay with this approach, I’m happy to open a PR.