HOST FIREWALL: A host-based firewall is software that runs directly on a networked device and protects that device against attack from the network by controlling incoming and/or outgoing network traffic. There are other kinds of firewalls that sit on the network between one or more hosts and the rest of the network, but their presence does not necessarily exempt protected devices from the need to run host-based firewall software. Host-based firewalls work by monitoring, passing, or blocking incoming and outgoing network packets. Rules govern what to look for and what to block or pass. Typical firewalls block based on source and destination address and port, packet type, etc. Advanced firewalls identify every application and system component, and rules to allow or block can be specific for each uniquely. A firewall product usually comes with predefined rules to defend against known attacks similar to anti-virus software, and predefined rules for each application and system component's normal activities. Rules may also just log the activity for later inspection or to send or display alarms. Some host-based firewalls can also prevent malicious software from attacking other devices on the network.