Firewall has a feature that makes it difficult to accidentally disable the system firewall. When you enable this feature the button that allows you disable the firewall is replaced with 'Can not Disable Firewall' and if you continue to try to disable the firewall, you may get a large error saying:
'Firewall can not be disabled'.
If you have come to this page to find out why you are getting this error, it is because someone has explicitly decided that the firewall must be turned on, and has created a lock file. It is suggested that you confer with your colleagues to find out why it should be on before disabling it.
This is enabled by creating a file called /etc/asterisk/firewall.lock (this can be done with the command 'touch /etc/asterisk/firewall.lock')
If you DO want to disable the firewall, you can either remove that file, and then click 'Disable', or, uninstall the firewall module.
This feature has been added due to numerous reports of machines getting hacked when the firewall was unexpectedly disabled by someone thinking Firewall was causing issues, and then not-re enabled.