Introduction to firewalls

Firewalls are computer security systems that
protect your office/home PCs or your network
from intruders, hackers & malicious code.
Firewalls protect you from offensive software
that may come to reside on your systems or
from prying hackers. In a day and age when
online security concerns are the top priority of
the computer users, Firewalls provide you with
the necessary safety and protection.
What exactly are firewalls?
Firewalls are software programs or hardware
devices that filter the traffic that flows into
you PC or your network through a internet
connection. They sift through the data flow &
block that which they deem (based on how &
for what you have tuned the firewall) harmful
to your network or computer system.
When connected to the internet, even a
standalone PC or a network of interconnected
computers make easy targets for malicious
software & unscrupulous hackers. A firewall
can offer the security that makes you less
vulnerable and also protect your data from
being compromised or your computers being
taken hostage.
How do they work?
Firewalls are setup at every connection to the
Internet, therefore subjecting all data flow to
careful monitoring. Firewalls can also be tuned
to follow "rules". These Rules are simply
security rules that can be set up by yourself or
by the network administrators to allow traffic
to their web servers, FTP servers, Telnet
servers, thereby giving the computer owners/
administrators immense control over the
traffic that flows in & out of their systems or
networks.
Rules will decide who can connect to the
internet, what kind of connections can be
made, which or what kind of files can be
transmitted in out. Basically all traffic in & out
can be watched and controlled thus giving the
firewall installer a high level of security &
protection.
Firewall logic
Firewalls use 3 types of filtering mechanisms:
Packet filtering or packet purity
Data flow consists of packets of information
and firewalls analyze these packets to sniff out
offensive or unwanted packets depending on
what you have defined as unwanted packets.
Proxy
Firewalls in this case assume the role of a
recipient & in turn sends it to the node that
has requested the information & vice versa.
Inspection
In this case Firewalls instead of sifting through
all of the information in the packets, mark key
features in all outgoing requests & check for
the same matching characteristics in the inflow
to decide if it relevant information that is
coming through.
Firewall Rules
Firewalls rules can be customized as per your
needs, requirements & security threat levels.
You can create or disable firewall filter rules
based on such conditions as:
IP Addresses
Blocking off a certain IP address or a range of
IP addresses, which you think are predatory.
What is my IP address? Where is an IP
address located?
Domain names
You can only allow certain specific domain
names to access your systems/servers or allow
access to only some specified types of domain
names or domain name extension like .edu
or .mil.
Protocols
A firewall can decide which of the systems can
allow or have access to common protocols like
IP, SMTP, FTP, UDP,ICMP,Telnet or SNMP.
Ports
Blocking or disabling ports of servers that are
connected to the internet will help maintain
the kind of data flow you want to see it used
for & also close down possible entry points for
hackers or malignant software.
Keywords
Firewalls also can sift through the data flow
for a match of the keywords or phrases to
block out offensive or unwanted data from
flowing in.
Types of Firewall
Software firewalls
New generation Operating systems come with
built in firewalls or you can buy a firewall
software for the computer that accesses the
internet or acts as the gateway to your home
network.
Hardware firewalls
Hardware firewalls are usually routers with a
built in Ethernet card and hub. Your computer
or computers on your network connect to this
router & access the web.
Summary
Firewalls are a must have for any kind of
computer usage that go online. They protect
you from all kinds of abuse & unauthorised
access like trojans that allow taking control of
your computers by remote logins or
backdoors, virus or use your resources to
launch DOS attacks.
Firewalls are worth installing. Be it a basic
standalone system, a home network or a office
network, all face varying levels of risks &
Firewalls do a good job in mitigating these
risks. Tune the firewall for your requirements
& security levels and you have one reason less
to worry.
Some of the firewall products that you may
want to check out are:
McAfee Internet Security
Microsoft Windows Firewall
Norton Personal Firewall
Trend Micro PC-cillin
ZoneAlarm Security Suit