How to block all the network traffic from my running user

Question

How to block all the network traffic from one user? But other users are alive to the network that the blocked user is able to connect to other users who have the permission to the internet.

Answer 1

You can block all outgoing network traffic for one user using the iptables owner module:

iptables -A OUTPUT -m owner --uid-owner <username> -j DROP
ip6tables -A OUTPUT -m owner --uid-owner <username> -j DROP

Note that this will block on all interfaces. If you want to use a specific interface, use -o <interface>.

You could also consider setting up another machine as the gateway to the network, and then requiring users to authenticate to it.