To block outgoing traffic to special 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, domain.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.
- 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.outNow modify /System/Library/LaunchDaemons/com.apple.pfctl.plist from
<array> <string>pfctl</string> <string>-f</string> <string>/etc/pf.conf</string> </array>
to
<array>
<string>pfctl</string>
<string>-e</string>
<string>-f</string>
<string>/etc/pf.conf</string>
</array>
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][1].
After a system update or upgrade some of the original files above may have been replaced and you have to reapply all changes.