Network Security - Firewalls
University of Phoenix
IT Infrastructure - CMGT 554
Firewalls are a portion of a network that provide protection for the system from the outside world, the Internet, or Cloud as well as provide a Network administrator the ability to monitor the packets, or requests trying to enter and leave the system or network that they are charged with. Not all firewalls are 100% foolproof; however operating a system without one is like leaving home for a long time and leaving the front door wide open inviting all to enter and take what they want or cause whatever mischief that is desire. A Firewall is akin to a lock on a door preventing unwanted visitors from entering. Its "key function is to legalize the stream of traffic among computers networks of different trust levels" (TopBits, 2010).
Firewalls can be hardware or software. Hardware firewalls usually fit between the company network and the modem connecting the network to the Internet. The external hardware devices provide high-level of defense from intrusion because they are separate devices and they provide their own operating environment that provides an extra line of defense (TopBits, 2010).
Basically four levels of firewalls exist, although not all firewalls fall into any one of any of these firewalls these categories (Boyer, 1997).
Stateful inspection firewall
A packet-filter can be a hardware or software mechanism that is configured to select packets from a traffic stream based on some criteria. This firewall accepts or rejects packets based on the information contained in the packets TCP and IP headers (WebHostGear, 2003). A lot business level IP routers, from Novell or Sysco Systems, are equipped packet-filter firewall capability.
This level of Firewall operates at the third or the "network layer" of the OSI model. The higher on the OSI model the firewall operates the more secure it tends to be; however, there is also a trade off in the speed and transparency of the firewall to the users. This level of firewall is relatively inexpensive and provides a relatively low-level of protection against hackers as this checks only the packet headers and an improper labeled packet can be passed through.
A Circuit-level gateway operates at the session-layer of the OSI. The circuit level gateway monitors the TCP handshake packets coming from trusted clients and un-trusted host to determine if a requested session is legitimate. To do this the gateway monitors the handshakes continually. This involves an exchange of packets flagged with SYN (synchronized) or ACK (acknowledge). These...