1. Host-Based Firewalls:
   1. Firewalls that run on a single host computer and controls network traffic in and out of a single host machine.
2. The default host-based firewall for each popular OS:
   1. Windows:
      1. Windows Firewall
      2. Windows Command Prompt:
         1. Access Windows Firewall:
            1. firewall.cpl
         2. Access Windows Firewall with Advanced Security:
            1. wf.msc
   2. MacOS X:
      1. PF (Packet Filter)
   3. Linux Kernel:
      1. iptables