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How Firewalls Mitigate Attacks

Network Security is the process by which digital information property are protected. In the event the network security is compromise, severe consequences could appear such as loss of private information [6]. To safeguard the networks the purpose of security should be maintain integrity, protect confidentiality and ensure availability [5]. To get started the network security process, you have to first develop security policy and access guidelines. This insurance plan must identify clearly the network security objectives of the business. Network Security includes security management, computer system security, data security, and network devices security [1].

Due to the incredible development of E-business and the internet all small or large organizations finding it very important to have web existence to compete nowadays. But connecting to the internet means that company's private network will be linked to the outside world [8]. This makes the private network vulnerable to attacks from the web. As in the case of E-business Company's web server must connect to the internet to provide WebPages to customers. This makes the net or file server susceptible to disorders. The network anatomist must defend the network against threats such as infections, worm, Trojan equine, fraud of information, misuse of resources, access control. Now a day's access to the Internet with no firewall is same as leaving your home door available to let anyone come inside. As the info theft or identify theft is all time high, computer systems networks need safeguard.

To provide defence from the intruders or hackers a special device was needed. That is why these devices called Firewall was launched in back 1988 [17]. Presently there are many different types of firewalls in the market. These firewalls not only different in expense but their functionalities are different as well. For an organization it is hard to pick up one firewall and considered covered against problems. This report explain you different types of firewalls and their features.

The following number shows the firewall is placed between the Internet and the private network to provide network security and protecting from problems.

Network Security Plan:

As everyone want to protect their network and the information in the network so we have to have some kind of rules to define that what is acceptable or what is not acceptable on the network [1]. To use these rules or procedures we first need to have a security coverage. Having a good and precise security is the excellent start of network security. After the creation of insurance policy we need execute this security policy to supply the complex control. Because if this hardware or software devices is required to provide the safeguard. A firewall is employed to apply this security insurance plan on the network

Securing Network with Firewall:

Technical settings are the main area of the network security program because it provides a cover against the problems and will keep network safe. Firewall is one of the key types of device to provide theoretically or actually control the network traffic.

What is a firewall:

The term firewall originally originates from firewalls which protect the hearth from distributing to the other area of the building[4]. A firewall is a tool in the network which split or isolate the dependable network (Private network) form the untrusted network (outdoors network). The firewall can be special devices such as hardware firewall or may be computer runing firewall software.

The primary goal of the firewall implementation is to protect the network from countless threats and only allow authoried traffic moving in or from the networks. Firewall can be used as standalone devices or can be configure on gateway router on the network such as Cisco PIX firewall [5].

The following amount display the firewall filtration traffic by enabling only approved traffic in the network and rejecting unauthorized traffic at the network boundary.

How Firewalls mitigate disorders?

The main aim of the firewall technology is to safeguard the hypersensitive information moving between the two networks [4]. In a real world situation firewall is placed between an exclusive network and internet to avoid episodes. Firewall is one of the very most essential barriers that can defend computer networks from many dangers. The firewall at the perimeter of the network is the first line of defence against exterior problems. To mitigate the episodes the firewall divides the network into two zones:

Trusted Area: authorized users in the private network or a private network.

Least trusted Zone: users from the Internet trying to gain access to the private network.

The simple firewall job is to either permit or refuse the traffic predicated on the access guidelines [4].

Permit: the certified traffic is allowed in the network in line with the predefined access rules.

Deny: the unauthorized traffic visit the firewall and information is delivered to network administrator or discarded.

The above physique shows that hoe firewall filtering the traffic based on the specified standards.

Protecting network with Firewall:

Firewalls filter the traffic transfers between two or more than two networks. It can split the network into covered or unprotected areas.

The firewall consider nearly as good firewall if it can protect network from pursuing vulnerabilities:

Firewall should provide coverage against problems from beyond your network. E. g. internet.

Firewall should protect the network from any kind of internal problems.

Firewall should offer access to the users based on the gain access to privilege level users posses [4].

Firewall should stop unauthorised users to gain access to the resources.

Hardware and Software Firewalls:

There are two main types of firewalls: Hardware firewall and Software firewall [5]. With regards to the network requirements different firewall can be used. Each one of these firewalls has its own benefits. Both of these firewalls have the same aim of providing the secure communication. In the organization you is it possible to either hardware or software or for better results mixture of hardware and software firewall can be used.

Hardware Firewalls:

As the name hardware make clear itself that it's a hardware firewall device. The hardware firewall is a special device which is generally placed near the gateway router of the network or between two networks to regulate the traffic move. Before positioning it on the network it is configure with the access policy or security rules on the firewall. When it activated on the network it regulates of the network traffic moving in or out of the network. The hardware firewall look at the incoming packet and equate to the access guidelines to decide either allow or discard the packet [11]. It is mostly used in large businesses and best suit for multinational companies.

The following amount shows the hardware firewall providing network security form the Internet.


Hardware firewall has different operating system which is the impartial of normal system such as Microsoft OS. Microsoft windows os's and other common OS have much vulnerability [11]. But hardware firewalls don't use common OS so that it is hard for attacker to own successful attack.

The other benefit for this is it faster than the other styles of firewalls and easy to put into action on the network [11].


The main disadvantage of the hardware firewall is that it's one point of failing. In case the hardware firewalls fail than all the traffic on the network will minimize. No traffic can go in or out of the network. The other downside is the fact that if attacker hack the firewall he can control the traffic going in or out of the network.

The most hardware firewalls cost more than the software firewall and specially trained personnel is required to manage these devices make the entire cost higher.

Also most of these hardware firewalls were created by different companies so that every of the needs different settings and maintenance. The network administrative needs to find out about that specific firewall before placing it into the network and will need to have understanding of how to manage the firewall deceive [11].

Software Firewalls:

Software firewall is a special software firewall program that may be install on the devices such as router, server or Computer. Once it is installed and configure properly it works that same manner as hardware firewall. It examines the traffic and allows or denies gain access to in line with the predefined access guidelines to determine whether the packet has authorization to gain access to the network or not.

The factor must be taken when installing the software firewall on the existing devices because software firewall heading to use the CPU and other resources on the devices [11]. Make certain the device have sufficient hardware resources to provide excellent performance in this environment. If there are not enough resources available for software firewall to use, this may impact the network performance.

Also as the problems and vulnerabilities changes because problems try different or new methods to episodes on the network so that the software firewall need to improved to supply the complete security against new risks on the sites. It is best suitable for smaller businesses and home systems. Because it is easy to implement and no special hardware is required.

The following shape shows the computer or router working the software firewall providing network security.


As the software firewall can be installed on the prevailing network devices so it normally cost less than the hardware firewall. There are numerous free software firewall programs on the internet which is often downloaded on the Computer for free.


Software firewalls discuss the system resources with other applications running on the computer. It could impact the performance of the computer if there are no enough resources.

Most of the times software firewall companies give free firewall program provide basic network protection only. To get the entire safeguard against all disorders you have to cover the progress services.

The other disadvantage of the program firewall is run on existing procedure system, so it can be quite vulnerable to have same king of attacks as on os's [11].

Different Types of Firewalls:

After defining both major categories of firewall, now the next part of the report describe the types of firewall based upon how firewall filtration packets and its own behaviour in the network security. In this record TCP/IP model is used to define the process of how packets are treated and filter by different kinds of firewalls.

Packet-filtering Firewall:

This was the first kind of firewall to safeguard the networks. Packet filtering firewall check the source and destination Ip of the packet and allow packets in or out in line with the security insurance plan of the business [8]. Normally gateway router on the network advantage is used to filtering these packets. Access control list (ACL) can be configured on the router to do something like packet filtering firewall. Predicated on the access rules router can allow or deny access in to the network.

The following amount displays the inbound approaching packet can be filter predicated on the specified guidelines such as Ip, packet types and port number.


It the simplest form of the firewall and easy to apply on the network. When Packet filtering firewall is placed in the network it will not decrease the network down and users of the network won't have the difference in network performance.


This was the first kind of firewall released for the systems. As it check the level 3 address in the packet and allow packet in or denied access according to the security policy. IP spoofing is strategy to spoof the IP address to any IP address you like to change. Hackers may use IP spoofing software to find the gain access to through the packet filtering firewall.

The other problem with packet filtering firewall is the fact it does not know who's using the service.

Recommended Usage:

Packet filtering firewall can be used in low security environment or when the price is an issue. It can be implemented on the router to save lots of money but this kind of firewall should not be used in high security environment. Best for small businesses or filter traffic within the organization.

Stateful Inspection Firewall

The stateful firewall inspections and monitors the state of the contacts between source and destination [4]. It is the most complex type of firewall. This type of firewall can monitor a myriad of contacts e. g. connection initiation, connection termination and information transfer [4]. It can perform the multilayer inspection. In multilayer inspection the packets first inspected at the Internet Protocol coating (Part 3 of the TCP/IP model) if the packet is granted access than additionally, it may perform the second check at the application form layer (Coating 5 of the TCP/IP model).

It can examine the TCP or UDP classes and keep screen these session between your source and vacation spot. Once the packet first attained the firewall it inspects the protocols in the packet and authorized or refused the packet based on the network security coverage. When the packet is authorized than it continues the info about the resources, destination, port number and TCP series amount in the record table. E. g. Cisco Pix firewall

The following figure displays the incoming approaching packet can be filtering based on the specified request rules.


It is more secure than the packet filtering since it will not only do the profound inspection of the packets but also maintains records of every session.


It can decrease the network down because all traffic goes through firewall which kind of firewall is expensive.

The other drawback is the when packet inside the network go outside the hackers can take the packet and examines the inner Ip in the packet header. This may give hacker some information about the Ip scheme used in the network. This information leads towards the some kind of assault on the network. But NAT can be used to resolve this problem with stateful firewall.

Recommended Utilization:

This kind of firewall is wonderful for systems that required higher level of security. Mostly employed by the medium and large size group where audit of each session is necessary.

Application-level Gateway

Application level firewall was design to provide more security to the network by examining all tiers of the TCP/IP model. As the packet switching firewall only examine the inbound packet up to Internet process part of but request coating firewall provide security examining up to program layer.

The software firewall is an ardent computer also known as proxy server. Proxy server proxy for exterior services obtain internal services and proxy exchange information with inside network [1]. The primary advantage is the fact it hides the inner network from the outsiders.

A proxy service has two important components: proxy ip server and proxy customer [3]

The job of the proxy ip server is to simply accept connection in one part of the network and connect to the other aspect of the network. Proxy Server first investigations if the connection or web host is allowed or not, if web host is allowed than the proxy server makes the next link with the destination web host on the far side of the network.

In this way the foundation host is linked indirectly to destination host via proxy ip server. This indirect connection between source and vacation spot conceal the valuable information about the inner network to spread to external network.


As Application coating firewall filter up to application later, it can understand variety of different software so that inspections can be perform on this content of the several software traffic for effect results.


If there are too many users in the network proxy services may decrease the network down.

The following amount displays the inbound approaching packet can be filtering based on the specified program rules. For example you can stop the HTTP traffic and allow all other protocol. With the application form firewall you have significantly more control to filtering traffic based on the protocols.

Recommended Usage:

This kind of firewall is wonderful for systems that required high level of security such as Banking. Mostly utilized by the medium and large size group. It cost more than the packet filtering firewall.

Circuit-Level Gateway

Circuit level firewall is more advance form of packet filtering firewall because it can take a look at the incoming packet in more detail. It also provides more safeguard against disorders as compare with packet filtering firewall. Circuit level firewall not only bank checks the IP address, port number but it addittionally checks the TCP handshake status between source and destination hosts and keep record of the TCP handshake [12]. This type of firewall assessments TCP handshake interconnection position before authorizing the access.

The circuit level firewall works at the TCP coating (Level 4 of TCP/IP model). Since it need to examines the TCP handshake between hosts and open up the procedure between hosts.

The source coordinator start the bond, when the packet arrived at the gateway; the gateway examines the connection information in the IP packet. The gateway find the match of the packet with the in security policy predefined on the gateway. If the packet gets authorization to enter in the network the gateway makes the next connection to the destination host. When the IP packet finds the vacation spot it has the source address as the address of the gateway [12].

The following amount exhibits the traffic is only allowed if the treatment is initiated by the approved number on the network usually all other traffic will be denied.


The circuit level gateway provides better safeguard against some disorders such as IP spoofing which packet filtering firewall cannot detect.

It inspections each TCP time and start the port manage all the inbound and outgoing interconnection. Due to that no unauthorized traffic allowed in the network it is considers covered network.

The other main circuit level gateway profit is the fact that it hides the Ip of the reliable network from the un-trusted systems because outside sponsor only get the source IP as the gateway address. E. g. Network Address Translation (NAT)


The main problem with this type of firewall is the fact that it does not check this content of the packet. Which means that the in the packet this content may be some kind of computer virus or worm. As a result of this reason authorized coordinator mistake may bring computer virus in the network.

Recommended Utilization:

This kind of firewall is wonderful for sites that required advanced of security. Mainly used by the medium and large size group. Network router can be used to become a firewall but also for large organizations separate firewall devices is preferred.

Comparison between different firewalls:

Firewall type or cost vary depends upon how big is the business and type or gain access to required. My exploration is based upon for medium size company. Now a day firewalls are incredibly advance device that has most the function in a single device. E. g. IDS, IPS

Hardware firewall

So many types can be purchased in market, depend on the sort can filter structured after IP address

Yes it can

Depends after the security policy the firewall can filtering inbound or outgoing traffic.

These are typically proprietor devices so the network administrator must learn to manage.

Cisco ACE 4710 HARDWARE-0. 5GBPS-100


Expensive since it includes the special hardware device.

Software firewall


Yes it can filter

Yes it is simple to use.

Cisco PIX Firewall Software


Relatively cheaper that hardware firewall

Packet filtering firewall



Basic firewall cannot filtration ports.

If configure to filter it can check either inbound or outgoing or both traffic.

Yes it is straightforward to use.

Netgear SRX5308-100EUS ProSafe Quad WAN Gigabit SSL VPN Firewall


One of the essential type, you will get this firewall cheaper.

Stateful firewall





Cisco ASA 5505 Security equipment - Unrestricted Firewall Release Bundle

441. 36

Expensive but provide good degree of protection

Application level firewall



Easy to manage GUI based interface rendering it to configure

SonicWALL NSA 220

644. 00

Expensive but provide good level of protection

Circuit level firewall




Easy to control GUI based software rendering it to configure

Cisco ASA 5505 Firewall Release Bundle - security appliance

566. 15

Expensive but provide good level of protection

Recommendation and Execution:

Firewall design concepts:

The first thing to keep in mind that firewall is good only when it is configured properly but before buying and putting the firewall in the network you need to know the solution of the next questions.

What kind of network it is and what are the network requirements?

What is kind of information you have in the network?

What level of protection is necessary?

Where to place the firewall in the network?

Firewall Basing:

There are many selections to put the firewall in the network. The next area of the report clarifies the best keeping the firewall.

Bastion Host

The bastion web host is a computer system that is employed on the network especially on the local area network. It really is normally installed after the first firewall. This system is designed so that all the traffic has to proceed through it. As all communication of the private LAN proceed through it was created to harden against problems from outdoors. It works the secure version of operating system and record of the audit information [18].

The following physique displays the bastion host in the network. All traffic in or from the private LAN is going through the bastion coordinator.

Figure 11 Bastion sponsor example [Ref: 13]

Host-Based Firewalls

The host structured firewall is designed to protect the individual host in the network [4]. This kind of firewall typically used for the servers [18] or other important variety in the network to provide another coating to defense resistant to the attacks. Host founded firewall normally comes with the operating-system or because it is software structured so you can also buy and install on the number.

This is the most effect solution to prevent the individual host in the network. Because most of the attacks now a day's comes from the within of the business network. So the firewall at the boundary cannot protect from these internal problems. By setting up the host established firewall on coordinator can defend web host against security violation and control the traffic according to the access rules. Since it is on the web host itself it can protect web host from both inside and external problems. The other advantage of host structured firewall is that it can be designed and configure based on the host requirement. The reason is that as some host on the network has different operating-system or different needs e. g. servers.

The disadvantage to get host structured firewall on web host is that web host procedures each packet which is CPU intense. This traffic checking process can decrease the performance of the individual host.

The following shape display each host in the network has host-based firewall to gives extra cover to the average person host according to their needs.

Figure 12 Coordinator structured Firewall [Ref: 14]

Personal Firewall

It is request software that can be installed using the pc or sponsor. Once activated using the pc it examines the traffic going in or from the computer. Customer control this firewall through GUI based application and configures the mandatory degree of security. It could allow or refuse the traffic as identified by an individual. There are several free personal firewalls on the internet which is often downloaded from the web. E. g. AVG antivirus is free and includes basic personal firewall.

The other thing you must remember that it is design to safeguard one host, which means that personal firewall need to install on every host on the network. This isn't very scalable in the top network that is why it's mostly use for computers in homes or for small office.

The following physique display the exemplory case of the Norton personal firewall.

Figure 13 Personal Firewall Example [Ref: 15]

Firewalls in network design:

There are extensive solutions available here are some of the key ones:

Demilitarized Area (DMZ) design:

The Demilitarized Zone (DMZ) is the special area which is designed between two sites. DMZ provides safeguard against outside and inside attacks. The exterior firewall is utilized to safeguard the network and the internal firewall is utilized protect the network from inside problems; the secure area is created between your two firewalls. Inside the large organizations this area can be used to keep carefully the servers such as web server or document servers so that the certified outside users can access the network. In really you are creating three zones:

Outside area (Internet)

Intermediate area (DMZ)

Inside zone (Private network)

You can easily see from the number below that two firewalls are use to create DMZ.

Figure 14 Firewall Execution in DMZ design [Ref: 17]

Fault tolerant firewall design:

The pursuing design may be used to provide fault tolerant solution. In the next design two firewalls are widely-used. Among the firewall is active method (main firewall) and the other is passive setting (standby firewall). If the productive firewall fails the unaggressive firewall takes control. This is best answer to supply the network security and redundancy.

Figure 15 Exemplory case of mistake tolerant firewall implementation [Ref: 16]

Test the firewall:

After firewall is installed in the network, you should test that how result it is and what exactly are the vulnerabilities of this firewall. Screening the firewall can be carried out by using the network assessment tools such as network penetration tools or Dock scanning tools. These tools can be purchased in the BackTrack software version 5 for network evaluation. If you able to hack you possess network and bypass the firewall, its means that firewall works well. In this manner you can able to find the vulnerabilities of the firewall and focus on these weaknesses to solve the network security issue.

Overall benefits and limitations of firewalls:

Benefits of using firewall in the Network:

Prevent unauthorized personals in the network.

Prevent hypersensitive information contact with unauthorized hosts.

The circulation of data between two networks or between two hosts can be operated.

By the deep examination of the data packet certain protocols can allowed or refuse in the network.

Security policy rules can be configuring to provide specialized control.

As all the network traffic goes through firewall, putting the firewall at the edge of the network provides one point of access for those data. It creates easy to control one point control connection to outside the house world.

Limitations of Firewalls:

As firewall is the sole point of entrance for everyone traffic, failure of firewall can cause the disconnection from the web or other linked networks.

Some of the new episodes may not be recognized by the firewalls.

Hackers try various ways to bypass the firewalls by examining the weakness or vulnerabilities of the specific firewall and assault in line with the type of firewall.

By inserting the firewall on the network advantage can decelerate the network performance because firewall has to check each packet moving in to out of the network.

If the firewall construction is not right it may well not stop the problems.

If the packet is encrypted firewall cannot understand


There is nobody firewall which is often positioned on the network and network will be 100% secure. So do not rely on just one single firewall to provide all kind of cover. Inside the network use multiple security devices such as IPS or IDS with the firewall to defence against other disorders. The most important to possess network security plan and all users must agree to follow this coverage. The firewall devices must be configured according to the security plan of the business. The network administer should regularly review the firewall as the amount of the threats changes frequently. The best firewall should decrease the risk of episodes and easier to manage setting. The cost is another important point when choosing the firewall. Finally when choosing the firewall network requirements, quality of service and performance should be the main consideration since it is the center point for the traffic moving in or from the network. Too many users and extra weight on the firewall can degrade the performance of the complete network. So during selection of the firewall thought of network requirements is the main stage.

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