Answer to Question 1
A firewall is software or a hardwaresoftware combination that is installed in a network to control the packet traffic moving through it. Most organizations place a firewall at the Internet entry point of their networks. The firewall provides a defense between a network and the Internet or between a network and any other network that could pose a threat.
Those networks inside the firewall are often called trusted, whereas networks outside the firewall are called untrusted. Acting as a filter, firewalls permit selected messages to flow into and out of the protected network. For example, one security policy a firewall might enforce is to allow all HTTP (Web) traffic to pass back and forth but disallow FTP or Telnet requests either into or out of the protected network. Firewalls can separate corporate networks from one another and prevent personnel in one division from accessing information from another division of the same company. Using firewalls to segment a corporate network into secure zones serves as a coarse need-to-know filter.
Answer to Question 2
The passwords that users select can be the source of a threat. Users sometimes select passwords that are guessed easily, such as their mothers maiden name, the name of a child, or their telephone number. Dictionary attack programs cycle through an electronic dictionary, trying every word and common name as a password.