Netgear Cable/DSL ProSafe Firewall FR328S User Manual download pdf (Page 107)

FR328S ProSafe Firewall with Dial Back-Up Reference Manual v2

Networks, Routing, and Firewall Basics B-11

M-10207-01, Reference Manual v2

What is a Firewall?

A firewall is a device that protects one network from another, while allowing communication

between the two. A firewall incorporates the functions of the NAT router, while adding features for

dealing with a hacker intrusion or attack. Several known types of intrusion or attack can be

recognized when they occur. When an incident is detected, the firewall can log details of the

attempt, and can optionally send email to an administrator notifying them of the incident. Using

information from the log, the administrator can take action with the ISP of the hacker. In some

types of intrusions, the firewall can fend off the hacker by discarding all further packets from the

hacker’s IP address for a period of time.

Stateful Packet Inspection

Unlike simple Internet sharing routers, a firewall uses a process called stateful packet inspection to

ensure secure firewall filtering to protect your network from attacks and intrusions. Since

user-level applications such as FTP and Web browsers can create complex patterns of network

traffic, it is necessary for the firewall to analyze groups of network connection states. Using

Stateful Packet Inspection, an incoming packet is intercepted at the network layer and then

analyzed for state-related information associated with all network connections. A central cache

within the firewall keeps track of the state information associated with all network connections.

All traffic passing through the firewall is analyzed against the state of these connections in order to

determine whether or not it will be allowed to pass through or rejected.

Denial of Service Attack

A hacker may be able to prevent your network from operating or communicating by launching a

Denial of Service (DoS) attack. The method used for such an attack can be as simple as merely

flooding your site with more requests than it can handle. A more sophisticated attack may attempt

to exploit some weakness in the operating system used by your router or gateway. Some operating

systems can be disrupted by simply sending a packet with incorrect length information.

Ethernet Cabling

Although Ethernet networks originally used thick or thin coaxial cable, most installations currently

use unshielded twisted pair (UTP) cabling. The UTP cable contains eight conductors, arranged in

four twisted pairs, and terminated with an RJ45 type connector. A normal straight-through UTP

Ethernet cable follows the EIA568B standard wiring as described below in Table B-1

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Netgear Cable/DSL ProSafe Firewall FR328S User Manual Page 107