Details
While in Stealth mode the computer will not respond to unsolicited probes, dropping that traffic.
http://support.apple.com/en-us/HT201642
Rationale:
Stealth mode on the firewall minimizes the threat of system discovery tools while connected to a network or the Internet.
Impact:
Traditional network discovery tools like ping will not succeed. Other network tools that measure activity and approved applications will work as expected.
This control aligns with the primary macOS use case of a laptop that is often connected to untrusted networks where host segregation may be non-existent. In that use case hiding from the other inmates is likely more than desirable. In use cases where use is only on trusted LANs with static IP addresses stealth mode may not be desirable.
Solution
Perform the following to implement the prescribed state:
Open System Preferences
Select Security & Privacy
Select Firewall Options
Select Enable stealth mode
Alternatively:
Run the following command in Terminal:
sudo /usr/libexec/ApplicationFirewall/socketfilterfw –setstealthmode on
Additional Information:
http://osxdaily.com/2015/11/18/enable-stealth-mode-mac-os-x-firewall/
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Unix.