killswitch, in a nutshell, once enabled, it will allow only traffic within the VPN, if the VPN goes down or it crashes, your traffic / IP address will not become exposed.
Before enabling the kill switch
killswitch -e the VPN needs to be up and running.
By just running
killswitch, information about the existing interfaces and
public IP address is printed. Example:
$ killswitch Interface MAC address IP en1 ac:21:37:b1:81:b4 192.168.1.50 Public IP address: 18.104.22.168 No VPN interface found, verify VPN is connecte
killswitch is executed, it will try to obtain the public IP address
via DNS or HTTP, if they differ both IP’s will be printed, example:
$ killswitch Interface MAC address IP en1 ac:21:37:b1:81:b4 192.168.1.50 DNS leaking: Public IP address (DNS): 22.214.171.124 Public IP address (WWW): 126.96.36.199 No VPN interface found, verify VPN is connected
See more: https://en.wikipedia.org/wiki/DNS_leak
Once VPN is up and running, run:
$ sudo killswitch -e
If VPN crashes or disconnects you may not be available to reconnect again unless you disable the kill switch.
WARNING Before disabling the kill switch, ensure you don’t have any application “P2P” running that may compromise your traffic/IP.
$ sudo killswitch -d
This will load the default firewall rules defined on
/etc/pf.conf. After doing this you may try to connect again the VPN and re-enable the kill switch.
Custom rules may be loaded by using something like:
$ sudo pfctl -Fa -f /etc/custom-pf.conf