D-Link DSL-504 [47/72] Enhanced security features

DSL-504 ADSL Router User’s Guide

Enhanced Security Features

Network security is an unfortunate necessity for any network connected to the

Internet. Protection of sensitive information and proprietary assets on your

private network should be designed into the network infrastructure from the

beginning. If you are not already, it is recommended that you become familiar

with network security issues and the strategies available to help reduce risks

from outside as well as from within your LAN. The Router provides features that

can enhance your network security and should be used in concert with other

security provisions, such as virus scanning software for all workstations, the use

of proxy servers and stateful inspection methods.

Advanced Filtering and Firewall

One of the most important elements of any network security implementation is

the firewall. Packet filtering is a basic firewall security measure that should be

used on any network that is exposed to security risk. A packet filter system

examines data packets and scrutinizes them for the purpose of controlling

network access. Filtering rules determine whether or not to allow access through

the Router from either side of the gateway. The rules are created and controlled

by the network administrator and can be precisely defined. These rules are used

to block access to the network from the outside, or deny access to the WAN from

within the network. The Router uses filtering rules to examine data packet

headers for specific information. Packets passing through the Router that do not

meet the criteria specified by the rule set are dropped.

In order to improve network security without severely limiting network

efficiency, it is important to carefully plan the sets of access rules. Effective

implementation of packet filtering requires detailed knowledge of network

services and communication protocols. An overly complicated filtering scheme

can adversely effect routing performance, while an inadequate set of rules may

needlessly compromise security.

Packet filtering can be used in conjunction with NAT, port redirection and proxy

servers to help provide basic firewall protection. However, these measures do not

address many security issues and should be used as only one part of an overall

network security strategy. It is important to remember that IP packet filtering

examines only the packet header and is not concerned with application

information. Therefore, packet filtering does not protect against higher-level

security threats that may operate at the application or other level.

Filtering rules can be precisely defined based upon source and destination IP

address, as well as port and protocol information. Up to twelve filter sets can be

used; each set contains up to seven filtering rules subsets.