The Ubuntu help wiki page on UFW says that UFW is a configuration tool for iptables. (In turn, the help wiki page on firewalls says that iptables is the database of firewall rules, and that it is also the actual firewall, as though a database is a firewall, which is obviously false. And of course 'iptables' is also the name of a program.)

iptables is not a service, but a facility inside the kernel. That is why you can't stop it. If you ever need to stop iptables quickly, here's my suggestion: Configure your iptables to completion. Save the configuration first: iptables-save > /etc/iptables.conf Flush the iptables, and configure it 'open': Iptables Tutorial: Ultimate Guide to Linux Firewall Jan 28, 2020 How to Use UFW Firewall on Debian, Ubuntu, Linux Mint Apr 03, 2020

The iptables-persistent looks for the files rules.v4 and rules.v6 under /etc/iptables. These are just a few simple commands you can use with iptables, which is capable of much more. Read on to check on some of the other options available for more advanced control over iptable rules.

How to Stop and Disable Firewall on CentOS 8

Had you searched this on google, the very first link would have answered your question. Had you asked this on stack exchange, they would have down voted this question and your reputation points would fall down as this shows that this question has

iptables is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. This module does not handle the saving and/or loading of rules, but rather only manipulates the current rules that are present in memory. This is the same as the behaviour of the iptables and ip6tables command which this module uses How to enable and disable the firewall on Ubuntu 16.04