How to Use Terminal for "Little Snitch" Functionality without Little Snitch
To permanently block outgoing traffic to specific domains you should create a new anchor file and add it to pf.conf.


Create an anchor file org.user.block.out in /private/etc/pf.anchors 

sudo touch /private/etc/pf.anchors/org.user.block.out


with the following content and a trailing empty line

mybadhosts = "{ www.domain.com, domain.com, www.domain2.com, domain2.com }"
mybadports = "{ 443, 80 }"

block drop out proto tcp from any to $mybadhosts port $mybadports


The additional domain names in mybadhosts are just an example how to add additional domains. The same goes for port 80 in mybadports.

A simple but less flexible solution is:

block drop out proto tcp from any to domain.com port 443

Modify the file /private/etc/pf.conf but keep a trailing empty line

original file:

scrub-anchor "com.apple/*"
nat-anchor "com.apple/*"
rdr-anchor "com.apple/*"
dummynet-anchor "com.apple/*"
anchor "com.apple/*"
load anchor "com.apple" from "/etc/pf.anchors/com.apple"


to

scrub-anchor "com.apple/*"
nat-anchor "com.apple/*"
rdr-anchor "com.apple/*"
dummynet-anchor "com.apple/*"
anchor "com.apple/*"
anchor "org.user.block.out"
load anchor "com.apple" from "/etc/pf.anchors/com.apple"
load anchor "org.user.block.out" from "/etc/pf.anchors/org.user.block.out"

Parse and test your anchor file to make sure there are no errors:

sudo pfctl -vnf /etc/pf.anchors/org.user.block.out

Now modify /System/Library/LaunchDaemons/com.apple.pfctl.plist from 

&lt;array&gt;
    &lt;string&gt;pfctl&lt;/string&gt;
    &lt;string&gt;-f&lt;/string&gt;
    &lt;string&gt;/etc/pf.conf&lt;/string&gt;
&lt;/array&gt;


to

&lt;array&gt;
    &lt;string&gt;pfctl&lt;/string&gt;
    &lt;string&gt;-e&lt;/string&gt;
    &lt;string&gt;-f&lt;/string&gt;
    &lt;string&gt;/etc/pf.conf&lt;/string&gt;
&lt;/array&gt;


You have to disable System Integrity Protection to accomplish this. After editing the file reenable SIP. After rebooting your Mac pf will be enabled (that's the -e option).

Alternatively you may create your own launch daemon similar to the answer here: Using Server 5.0.15 to share internet WITHOUT internet sharing.


After a system update or upgrade some of the original files above may have been replaced and you have to reapply all changes.