Firewall
The firewall is the most important method for keeping a
computer secure from invaders. Use the firewall to allow or block
traffic into and out of the user's computer. Firewalls facilitate
secure access the Internet as well as to separate a company's public
Web server from its internal network. Here are different firewall
techniques:
Packet filter:
Looks at each packet entering
or leaving the network and
accepts or rejects it based on user-defined rules.
Packet filtering is
fairly effective and transparent to users, but it is difficult to
configure. In addition, it is susceptible to IP spoofing.
Application gateway:
Applies security
mechanisms to specific
applications, such as FTP and Telnet servers. This is very effective,
but can impose a performance degradation.
Circuit-level gateway:
Applies security
mechanisms when a TCP or UDP
connection is established. Once the connection has been made, packets
can flow between the hosts without further checking.
Proxy server:
Intercepts all messages entering
and leaving the network.
The proxy server effectively hides the true network addresses.
Many firewalls use two or more of these methods. A
firewall is only a first line of defense. There is also data encryption
and regular virus
scans.
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