How to whitelist output traffic on Linux?

Question

linux

I would like to deny access to the Internet to all programs, except for a few (by the name of the process, or, better, by the process ID). Those will run proxies on the locale, and if the program wants the Internet, let it use this proxy, otherwise its problems. I heard that firewalls are used for this. For example, iptables. But I don’t know the specific addresses with which darknets will connect. How to act here?

Answer 1

The -m owner module also has the key "--pid-owner"
/sbin/iptables -A OUTPUT -o eth0 -m owner --pid-owner 1000 -j DROP