Securing System Using Iptable Firewall

Running head: SECURING SYSTEM USING IPTABLE FIREWALL
Securing system using IPTable firewall
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Introduction
Along with the increased accessibility to the internet and the administrator of the
system creates filtering rules chains in which the order is significant. Therefore in order to
protect network devices, organizational network in order to protect both the organizational
data as well as individual data it is important to have well configured firewall in place. The
Linux operating system comes with the inbuilt firewall that can be used to protect the
computer systems from unintended intrusions. With the benefits there are some draw backs
of this firewall too. The iptable firewall needs to be configured by the system administrators.
With misconfigured firewalls it is possible to unintentionally create backdoors for the
attackers which can lead to the massive data breach or network attacks carried out by the
attackers.
This means that insertion or removal of different rules in inappropriate order leads to
errors. In addition to that, as the size and number of the data packets or chains determines the
complexity of any kind of rule set, thus it can be stated that iptable firewall consisting too
many large chains of rules becomes very difficult to understand as well as modify them at a
later time. In many of the cases it becomes difficult to know the important requests that are
granted to pass within the firewall filter.
In any network the firewalls have become a foundation for the basic security
implementation against the external attacks to the certain networks along with the many
security policies. The rules and policies used in the firewalls has been grown in complexity in
order to secure the networks from different attacks. Along with the packet filtering process
the typical firewall is now capable of providing state full inspection of the data packets.
Among different other drawbacks of the firewalls one of the most important is the
growing complexity in correctly configuring a specific firewall with the appropriate rule set.

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Subtle errors in the configuration of the firewalls may be very challenging to detect among
the lots of rule chains. The subtle error can be responsible for opening a backdoor for the
malicious intruder so that they can carry out denial of service attack or similar other attacks.
The iptables firewall of Linux operating system protects a computer network through
the comparison of the data packets coming through the network traffic against some
implemented rules. These implemented rules are the characteristics that a data packet needs
to match in order to get into the network or dropped out of a certain network or any other
action that needs to be taken for the data packets that are matching with the implemented
rules. These implemented rules are structured in different groups which are known as the
chains. A received packet to a network is checked against the chain or the set of rules
sequentially. Whenever the received data packet matches with one of the implemented rules,
it start executing the associated action declared for the rule and furthermore is not verified
against others rules of the chain.
There are numerous options so that it can be established which packets match a
specific type of rule. The implemented rules of the firewall can match protocol type from
which the packet is coming, source/destination ip/port, interface used for sending the data
packet as well as relation with the previously sent data packets and so on.
Whenever any of the defined pattern/rules matches with the data packets, the
specified actions takes place which is one of drop the packet, allow the packet to the network.
In addition to that, this policies can also move the data packet to different other rule sets for
further processing or log the occurrence in the concerned log files.
Utility of Iptables
The firewalls are frequently introduced away from the rest of the computer networks
so no approaching data packets or request get legitimately to the secured network resources.

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In the event that it is designed appropriately, the other side framework of the firewall are
guarded from the opposite direction framework. Firewalls for the most part channel traffic
dependent on two procedures:
 A firewall can grant any traffic aside from what is designated as limited. It
actually depending on the utilized firewall type, the goal address, the sources
and the ports.
 A firewall can reject any traffic which is not meeting the particular criteria
dependent on the system layer. Depending on this system layer the firewall
executes.
 These criteria are mainly utilized for determining whether the traffic should be
allowed through changes from one kind to another.
 Firewalls can be concerned about the type of traffic or with the goal or source
locations and ports.
 A firewall is capable of using complex guidelines dependent on application
information investigation for deciding whether the traffic ought to be allowed
through.
The majority of the iptable packet filters follow the principle of first-hit. Each of the
rule defined in the rule set is consisting different types of parameters which mainly
correspond to the network packet headers. All of the packets, traversing within firewall is
matched against the rules defined in filtering table. In this aspect, the rule of which
parameters are having the similar values with the packet parameters under matching progress
is applied to it. This instance decides whether it better to let the packet go further or it is
better to just drop it. Specific rules which are succeeding the rule which is being matched are
not accounted. In such of the incidents when the rule is not discovered, the global rule from