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Network security is a complicated subject, historically only tackled by welltrained and experienced experts. However, as more and more people become``wired'', an increasing number of people need to understand the basics of security in a networked world. It explains the concepts needed to read through the hype in the marketplace and understand risks and how to deal with them. Some history of networking is included, as well as an introduction to TCP/IP and internetworking. We go on to consider risk management, network threats, firewalls, and more special-purpose secure networking devices. This is not intended to be a ``frequently asked questions'' reference, nor is it a ``hands-on'' document describing how to accomplish specific functionality. It is hoped that the reader will have a wider perspective on security in general, and better understand how to reduce and manage risk personally, at home, and in the workplace.
The computer is the great invention of 20th century which has been nowthe part of our life. Gradually it became necessary to connect different computers that lead to establish local network. The network field grew up by leaps and bound that lead to huge matrix of computer network. This great invention is known as Internet. It benefited to human being in each & every field, which is now part of our life. But as we know each coin has two sides. Similarly the darkness of network field is an unimaginable. For example whenever you connect to your internet, you provide Gateway to the hackers & crackers who are wiling to enter your machine thus whenever you connect to internet your machine is not secure at all. Now the big Q is how to provide protection to your machine & secure our data & information The only answer is Network Security.
To secure your machine is the first rule of todayâ„¢s cyber world but securing your network is as just imp9ortant as in todayâ„¢s cyber world. There is not need to physical access to be completely in control. Network security is the utmost importance to everyone. Network security is indeed the hot topic of discussion amongst all computers enthusiastic & it has also become a major concern in broad room across the globe. Companies have started taking computer security very seriously and dedicated teams who maintain & secure the companies sensitive information round the clock. Even individuals who use ultimate tool the internet have started to show an increase4d demand for
tools or ways to protect their system against criminal. It is totally impossible to create 100% foolproof firewall or network without compromising the services that network has offer being aware and regularly updating oneâ„¢s network in tune with latest updating in field of computer security, is one trick that internet user must have in his or her armory of defense against computer infiltration.
In an era where a single click of mouse is potent enough to lead to a full fledged attack. The increase security of oneâ„¢s network is no longer luxury that everyone enjoys but it has become necessary.

Seminar By:
Ashwini Ashok Joga

Sr No Topic
Page No
1 Abstract 3

2 Introduction 4

3 Internet 6

4 TCP/IP 10

5 Attacks against IP 11

6 Types n sources of N/W threats 14

7 Security Measures 18

8 Firewalls 20

9 Conclusion 23

10 References 24

A basic understanding of computer networks is requisite in order to understand the principles of network security. In this section, we'll cover some of the foundations of computer networking, then move on to an overview of some popular networks. Following that, we'll take a more in-depth look at TCP/IP, the network protocol suite that is used to run the Internet and many intranets.
Once we've covered this, we'll go back and discuss some of the threats that
managers and administrators of computer networks need to confront, and then
some tools that can be used to reduce the exposure to the risks of network
What is a Network
A ``NETWORK'' has been defined as ``any set of interlinking lines resembling a net, a network of roads an interconnected system, a network of alliances. ''This definition suits our purpose well: a computer network is simply a system of interconnected computers. How they're connected is irrelevant, and as we'll soon see, there are a number of ways to do this.

The ISO/OSI Reference Model:-
The International Standards Organization (ISO) Open Systems Interconnect
(OSI) Reference Model defines seven layers of communications types, and the
interfaces among them. (See Figure 1 Each layer depends on the services
provided by the layer below it, all the way down to the physical network hardware, such as the computer's network interface card, and the wires that connect the cards together.
An easy way to look at this is to compare this model with something we use daily: the telephone. In order for you and me to talk when we're out of earshot, we need a device like a telephone. (In the ISO/OSI model, this is at the application layer.) The telephones, of course, are useless unless they have the ability to translate the sound into electronic pulses that can be transferred over wire and back again. (These functions are provided in layers below the application layer.) Finally, we get down to the physical connection: both must be plugged into an outlet that is connected to a switch that's part of the telephone system's network of switches.
If I place a call to you, I pick up the receiver, and dial your number. This number specifies which central office to which to send my request, and then which phone from that central office to ring. Once you answer the phone, we begin talking, and our session has begun. Conceptually, computer networks
function exactly the same way.
It isn't important for you to memorize the ISO/OSI Reference Model's layers;
but it's useful to know that they exist, and that each layer cannot work without
the services provided by the layer below it.
Network layer
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network layer
Data link Layer
Physical Layer
What are some Popular Networks
Over the last 25 years or so, a number of networks and network protocols have
been defined and used. We're going to look at two of these networks, both of which are ``public'' networks. Anyone can connect to either of these networks, or they can use types of networks to connect their own hosts (computers) together, without connecting to the public networks. Each type takes a very
different approach to providing network services.
The Internet:-

Figure 2
This is a word that We've heard way too often in the last few years. Movies,
books, newspapers, magazines, television programs, and practically every
other sort of media imaginable have dealt with the Internet recently. Today it
has been part of the human life. Our entire lives are based on the internet. It
has been proved an ultimate knowledge tool for human being.
What is the Internet
The Internet is the world's largest network of networks . When you want to
access the resources offered by the Internet, you don't really connect to the
Internet; you connect to a network that is eventually connected to the Internet
backbone , a network of extremely fast (and incredibly overloaded!) network
components. This is an important point: the Internet is a network of networks
-- not a network of hosts.

A simple network can be constructed using the same protocols and such that
the Internet uses without actually connecting it to anything else. Such a basic
network is shown in Figure 6.
It might be allowed to put one of my hosts on one of my employer's networks.
We have a number of networks, which are all connected together on a
backbone , that is a network of our networks. Our backbone is then connected
to other networks, one of which is to an Internet Service Provider (ISP) whose
backbone is connected to other networks, one of which is the Internet
If you have a connection ``to the Internet'' through a local ISP, you are actually
connecting your computer to one of their networks, which is connected to
another, and so on. To use a service from my host, such as a web server, you
would tell your web browser to connect to my host. Underlying services and
protocols would send packets (small datagrams) with your query to your ISP's
network, and then a network they're connected to, and so on, until it found a
path to my employer's backbone, and to the exact network my host is on. My
host would then respond appropriately, and the same would happen in reverse:
packets would traverse all of the connections until they found their way back
to your computer, and you were looking at my web page.

Figure 4: A Simple Local Area Network
In Figure 4,the network shown in Figure 3is designated ``LAN 1'' and shown
in the bottom-right of the picture. This shows how the hosts on that network
are provided connectivity to other hosts on the same LAN, within the same
company, outside of the company, but in the same ISP cloud , and then from
another ISP somewhere on the Internet.

Figure 5: A Wider View of Internet-connected Networks
The Internet is made up of a wide variety
of hosts, from supercomputers to
personal computers, including every imaginable type of hardware and
software. How do all of these computers understand each other and work
Following are some of the terms concerned with internet.
(Advanced Research Projects Agency Network) -- The precursor to the
Internet. Landmark packet-switching network established in 1969 by the US
Department of Defense as an experiment in wide-area-networking that would
survive a nuclear war.

Figure 6: The Birth of Arpanet

Figure 7: The Arpanet research scientists.
A high-speed line or series of connections that forms a major pathway within
a network. The term is relative, as a backbone in a small network will likely be
much smaller than many non-backbone lines in a large network
DNS: Domain Naming System:-
DNS stands for Domain Name System and is a distributed, replicated system
which allows name servers to map domain names to an IP number. DNS is
integral to the Internet in that it allows people to use hostnames (
rather than IP addresses ( in web, e-mail, and other Internet
A special-purpose computer (or software package) that handles the connection
between 2 or more networks. Routers spend all their time looking at the
destination addresses of the packets passing through them and deciding which
route to send them on.
TCP/IP: The Language of the Internet:-
TCP/IP (Transport Control Protocol/Internet Protocol) is the ``language'' of the
Internet. Anything that can learn to ``speak TCP/IP'' can play on the Internet.
This is functionality that occurs at the Network (IP) and Transport (TCP)
layers in the ISO/OSI Reference Model. Consequently, a host that has TCP/IP
functionality (such as Unix, OS/2, MacOS, or Windows NT) can easily
support applications (such as Netscape's Navigator) that uses the network.
As noted, IP is a ``network layer'' protocol. This is the layer that allows the
hosts to actually ``talk'' to each other. Such things as carrying datagrams,
mapping the Internet address (such as to a physical network address
(such as 08:00:69:0a:ca:8f), and routing, which takes care of making sure that
all of the devices that have Internet connectivity can find the way to each
other.Whenever one connect to the internet a unique address is given to that
system, this address is known as I.P Address.As quick one disconnect the I.P
address is changed.
Understanding IP:-
IP has a number of very important features which make it an extremely robust
and flexible protocol. For our purposes, though, we're going to focus on the
security of IP, or more specifically, the lack thereof.An I.P address is a 32 bit
address fragmented in four parts each having 8 bit address.There are mainly
five classes of I.P address as shown in figure.
Class Range
A -
B -
C -
D -
E -
Classes of I.P Address.
Thus from above table one can classify I.P address and determinate which I.P
Address belongs to which class.If your I.P address is 128.xx.xx.xx then it is
from class B etc.The various information that can be gathered from I.P address
is as shown in figure 6.
Class Information
A First 8 bit for Net-id, last 24 bit for Host-id.
B First 16 bit for Net-id, last 16 bit for Hostid.
C First 24 bit for Net-id, last 8 bit for Host-id.
D First 32 bit multicasting.
E For future use.
Attacks Against I.P
A number of attacks against IP are possible. Typically, these exploit the fact
that IP does not perform a robust mechanism for authentication , which is
proving that a packet came from where it claims it did. A packet simply claims
to originate from a given address, and there isn't a way to be sure that the host
that sent the packet is telling the truth. This isn't necessarily a weakness, per se
, but it is an important point, because it means that the facility of host
authentication has to be provided at a higher layer on the ISO/OSI Reference
Model. Today, applications that require strong host authentication (such as
cryptographic applications) do this at the application layer.
Obtaining IP address:-
The hackers can apply any approach to get victims IP address.
(1)Sometimes he may use IRC
(2) Sometimes he may run some malicious scripts to get IP address.
(3)One can attack through http.
(4)Through email headers.
(5)Using available Tip-top softwares.
IP Spoofing :-
IP spoofing is an exciting topic.It is a subject about which no more people
knows.This is where one host claims to have the IP address of another. Since
many systems (such as router access control lists) define which packets may
and which packets may not pass based on the sender's IP address, this is a
useful technique to an attacker: he can send packets to a host, perhaps causing
it to take some sort of action.
Additionally, some applications allow login based on the IP address of the
person making the request (such as the Berkeley r-commands). These are both
good examples how trusting untrustable layers can provide security that is -- at
best -- weak.IP spoofing is quite difficult to understand.Major problem is that
it can almost not be done using windows also the windows system
administrator can easily protect it from IP spoofing.
IP spoofing is a trick played on server to fool the target system to fool
the target system into thinking that it is receiving data from source other than
you.Thus it is a technique to fool the victim that data is send from a system
other than you.
Following example makes it clearer.
Let your IP address
Let the IP address of victim be
Spoofed address that victim get from you is fake.(other than real).
IP spoofing is a blind attack. In this process the attacker does not get any
information about the progress of the process.As here the attacker does not get
any ack message from the victim. As you have spoofed your IP address the
victim system sends an ack message to the fake IP address.Now suppose fake
IP addressâ„¢s system donâ„¢t give any response than the connection may be
lost.Without spoofing following three way handshake will take place.
IP Session Hijacking.
This is a relatively sophisticated attack, first described by Steve Bellovin .
This is very dangerous, however, because there are now toolkits available in
the underground community that allow otherwise unskilled bad-guy-wannabes
to perpetrate this attack. IP Session Hijacking is an attack whereby a user's
session is taken over, being in the control of the attacker. If the user was in the
middle of email, the attacker is looking at the email, and then can execute any
commands he wishes as the attacked user. The attacked user simply sees his session dropped, and may simply login again, perhaps not even noticing that
the attacker is still logged in and doing things.
For the description of the attack, let's return to our large network of networks
in Figure 4. In this attack, a user on host A is carrying on a session with host G.
Perhaps this is a telnet session, where the user is reading his email, or using
a Unix shell account from home. Somewhere in the network between A and B
sits host H which is run by a naughty person. The naughty person on host H
watches the traffic between A and G, and runs a tool which starts to
impersonate A to G, and at the same time tells A to shut up, perhaps trying to
convince it that G is no longer on the net (which might happen in the event of a
crash, or major network outage). After a few seconds of this, if the attack is
successful, naughty person has ``hijacked'' the session of our user. Anything
that the user can do legitimately can now be done by the attacker,
illegitimately. As far as G knows, nothing has happened.
This can be solved by replacing standard telnet-type applications with
encrypted versions of the same thing. In this case, the attacker can still take
over the session, but he'll see only ``gibberish'' because the session is
encrypted. The attacker will not have the needed cryptographic key(s) to
decrypt the data stream from G, and will, therefore, be unable to do anything
with the session.
Countermeasure against IP Hijacking:-

Fig 8
Following are some of the way through which one can secure Oneâ„¢s IP
(1)The easiest way to protect your privacy while surfing inline is by
connecting to various websites through an anonymous surfing services like or services will not only hide your IP address
but also hide information about your system, your browser name and
operating system name.
(2)Secondly anything that can do to protect you is to surf via an anonymous
proxy server A proxy server is basically a server which acts as a buffer
between source and host. All request that you send are filtered at the proxy
server.However the proxy server will hide only IP address not the information
like your operating system or browser name. For more detail on proxy read
Proxy section.
(3)Another sophisticated way is to connect through various anonymous
(4)If you truly want to remain anonymous while sending or receiving mails
use the anonymous mailing services.They will provide you completely
(5)One should be particular while opening an account for the email
services.Try and look for some services that provide you some sort of
(6)Use commands available to hide your identity on internet relay chat.
(7)Never accept any DDC request from people you donâ„¢t, know. Such attacks
are from malicious people or attackers.
(8)Another precaution is that use the use the only those IRC servers that hide
your identity on the internet.
(9)Another thing that to use the firewall that alerts you at each and every
incoming message.(for detail on firewall read firewall section).
TCP is a transport-layer protocol. It needs to sit on top of a network-layer
protocol, and was designed to ride atop IP. (Just as IP was designed to carry,
among other things, TCP packets.) Because TCP and IP were designed
together and wherever you have one, you typically have the other, the entire
suite of Internet protocols are known collectively as ``TCP/IP.'' TCP itself has
a number of important features that we'll cover briefly.
Types and Sources of Network Threats:-
Now, we've covered enough background information on networking that we
can actually get into the security aspects of all of this. First of all, we'll get into
the types of threats there are against networked computers, and then some
things that can be done to protect you against various threats.
DoS (Denial-of-Service) attacks are probably the nastiest, and most difficult to
address. These are the nastiest, because they're very easy to launch, difficult
(sometimes impossible) to track, and it isn't easy to refuse the requests of the
attacker, without also refusing legitimate requests for service.
The premise of a DoS attack is simple: send more requests to the machine than
it can handle. There are toolkits available in the underground community that
make this a simple matter of running a program and telling it which host to
blast with requests. The attacker's program simply makes a connection on
some service port, perhaps forging the packet's header information that says
where the packet came from, and then dropping the connection. If the host is
able to answer 20 requests per second, and the attacker is sending 50 per
second, obviously the host will be unable to service all of the attacker's
requests, much less any legitimate requests (hits on the web site running there,
for example).
Such attacks were fairly common in late 1996 and early 1997, but are now
becoming less popular.
The various dos attacks are describes as below.
(1) Ping of death:-
Usually in this type of attack the ping command is used to remotely login the
victimâ„¢s computer. For example the maximum size of data that can be
transmitted from TCP/IP packet is 65,536 bytes. Using ping command on can
send large amount of data to your network, which leads to the crash or hang up
of the system.
(2) Teardrop attack:-
In this kind of attack the sequence number of the packet is changed. Thus on
receiving side the system get confused which packet is right and which is
wrong. That leads to hang up.
(3) Sin flooding:-
Here the spoofing technique is used. The victim system wait for sin message
but as real address is not available the victim system gets hang up.
(4) Land attack:-
Same as sin attack but here instead of fake IP address the address of the
victim system itself is used.
(5) UDP flooding:-
In this type of attack infinite loop is created between the two UDP systems.
(6) Distributed Dos attacks:-
In this attack the more than two persons distribute attack on victim system.
Some things that can be done to reduce the risk of being stung by a denial of
service attack include
¢ Not running your visible-to-the-world servers at a level too close to
¢ Almost all new systems are bound not to be vulnerable to the Ping
¢ Reduce the time out session of a connection to take place.
¢ Installing vendor specific updates or by firewall that detect the SYN
flood attack.
¢ Using packet filtering to prevent obviously forged packets from
entering into your network address space.
¢ Disable the echo services that you really don™t need.
¢ Obviously forged packets would include those that claim to come from
your own hosts, addresses reserved for private networks as defined in
RFC 1918 , and the loop back network (
¢ Keeping up-to-date on security-related patches for your hosts'
operating systems.
Trojan attacks:-
It is a one kind of tool which when installed on the system can be used for
malicious purpose. by a attacker. It is a programmed that attacker install on the
target system with the help of trickery or by malicious Trojan code into a
trusted system or by having physical access to the target system.

Fig 9
There are two kinds of Trojans.
(a) Client side Trojans:-
Here the Trojan should be installed and running on the target system
(b) Server side Trojans:-
Here the Trojan should be installed and running on the attacker system
Countermeasures against Trojans:-

figure 10
(1) Trojans enter in the target system from specific ports. So compare the open
ports with the Trojan port numbers If any Trojan port is open close it.
(2) Never accept any file sent on internet,IRC,E-mail that is unknown.
(3) Download EXE files from the trusted sites only.
Unauthorized Access:-
``Unauthorized access'' is a very high-level term that can refer to a number of
different sorts of attacks. The goal of these attacks is to access some resource
that your machine should not provide the attacker. For example, a host might
be a web server, and should provide anyone with requested web pages.
However, that host should not provide command shell access without being
sure that the person making such a request is someone who should get it, such
as a local administrator.
Executing Commands Illicitly:-
It's obviously undesirable for an unknown and untrusted person to be able to
execute commands on your server machines. There are two main
classifications of the severity of this problem: normal user access, and
administrator access. A normal user can do a number of things on a system
(such as read files, mail them to other people, etc.) that an attacker should not
be able to do. This might, then, be all the access that an attacker needs. On the
other hand, an attacker might wish to make configuration changes to a host
(perhaps changing its IP address, putting a start-up script in place to cause the
machine to shut down every time it's started, or something similar). In this
case, the attacker will need to gain administrator privileges on the host.
Destructive Behavior:-
Among the destructive sorts of break-ins and attacks, there are two major
Data Diddling:-
The data diddler is likely the worst sort, since the fact of a break-in might not
be immediately obvious. Perhaps he's toying with the numbers in your spreadsheets, or changing the dates in your projections and plans. Maybe he's
changing the account numbers for the auto-deposit of certain paychecks. In
any case, rare is the case when you'll come in to work one day, and simply
know that something is wrong. An accounting procedure might turn up a
discrepancy in the books three or four months after the fact. Trying to track
the problem down will certainly be difficult, and once that problem is
discovered, how can any of your numbers from that time period be trusted
How far back do you have to go before you think that your data is safe
Data Destruction:-
Some of those perpetrate attacks are simply twisted jerks who like to delete
things. In these cases, the impact on your computing capability -- and
consequently your business -- can be nothing less than if a fire or other
disaster caused your computing equipment to be completely destroyed.
Where Do They Come From
How, though, does an attacker gain access to your equipment Through any
connection that you have to the outside world. This includes Internet
connections, dial-up modems, and even physical access. (How do you know
that one of the temps that you've brought in to help with the data entry isn't
really a system cracker looking for passwords, data phone numbers,
vulnerabilities and anything else that can get him access to your equipment)
In order to be able to adequately address security, all possible avenues of entry
must be identified and evaluated. The security of that entry point must be
consistent with your stated policy on acceptable risk levels.
Lessons Learned:-
From looking at the sorts of attacks that are common, we can divine a
relatively short list of high-level practices that can help prevent security
disasters, and to help control the damage in the event that preventative
measures were unsuccessful in warding off an attack.
Hope you have backups:-
This isn't just a good idea from a security point of view. Operational
requirements should dictate the backup policy, and this should be closely
coordinated with a disaster recovery plan, such that if an airplane crashes into
your building one night, you'll be able to carry on your business from another
location. Similarly, these can be useful in recovering your data in the event of
an electronic disaster: a hardware failure, or a breaking that changes or
otherwise damages your data.
Don't put data where it doesn't need to be:-
Although this should go without saying, this doesn't occur to lots of folks. As
a result, information that doesn't need to be accessible from the outside world
sometimes is, and this can needlessly increase the severity of a break-in
Avoid systems with single points of failure:-
Any security system that can be broken by breaking through any one
component isnâ„¢t really very strong. In security, a degree of redundancy is
good, and can help you protect your organization from a minor security breach
becoming a catastrophe.
Stay current with relevant operating system patches:-
Be sure that someone who knows what you've got is watching the vendors'
security advisories. Exploiting old bugs is still one of the most common (and
most effective!) means of breaking into systems.
Watch for relevant security advisories:-
In addition to watching what the vendors are saying, keep a close watch on
groups like CERTand CIAC. Make sure that at least one person (preferably
more) is subscribed to these mailing lists
Have someone on staff be familiar with security practices:-
Having at least one person who is charged with keeping abreast of security
developments is a good idea. This need not be a technical wizard, but could be
someone who is simply able to read advisories issued by various incident
response teams, and keep track of various problems that arise. Such a person
would then be a wise one to consult with on security related issues, as he'll be
the one who knows if web server software version such-and-such has any
known problems, etc.
This person should also know the ``dos'' and ``don'ts'' of security, from reading
such things as the ``Site Security Handbook.''
As we've seen in our discussion of the Internet and similar networks,
connecting an organization to the Internet provides a two-way flow of traffic.
This is clearly undesirable in many organizations, as proprietary information is
often displayed freely within a corporate intranet (that is, a TCP/IP network,
modeled after the Internet that only works within the organization).
In order to provide some level of separation between an organization's intranet
and the Internet, firewalls have been employed. A firewall is simply a group of
components that collectively form a barrier between two networks. The pure
definition of the firewall refers to the A software or hardware or the combination of the software and hardware that filters all the incoming

Fig 11
A number of terms specific to firewalls and networking are going to be used
throughout this section, so let's introduce them all together.
A special purpose computer for connecting networks together. Routers also
handle certain functions, such as routing , or managing the traffic on the
networks they connect.
Types of Firewalls:-
There are three basic types of firewalls, and we'll consider each of them.
Application Gateways:-
The first firewalls were application gateways, and are sometimes known as
proxy gateways. These are made up of bastion hosts that run special software
to act as a proxy server. This software runs at the Application Layer of our old
friend the ISO/OSI Reference Model, hence the name. Clients behind the
firewall must be prioritized (that is, must know how to use the proxy, and be
configured to do so) in order to use Internet services. Traditionally, these have
been the most secure, because they don't allow anything to pass by default, but
need to have the programs written and turned on in order to begin passing

Figure12: A sample application gateway
These are also typically the slowest, because more processes need to be started
in order to have a request serviced. Figure 10 shows a application gateway.
Packet Filtering:-
Packet filtering is a technique whereby routers have ACLâ„¢s (Access Control
Lists) turned on. By default, a router will pass all traffic sent it, and will do so
without any sort of restrictions. Employing ACLâ„¢s is a method for enforcing
your security policy with regard to what sorts of access you allow the outside
world to have to your internal network, and vice versa.
There is less overhead in packet filtering than with an application gateway,
because the feature of access control is performed at a lower ISO/OSI layer
(typically, the transport or session layer). Due to the lower overhead and the
fact that packet filtering is done with routers, which are specialized computers
optimized for tasks related to networking, a packet filtering gateway is often
much faster than its application layer cousins. Figure 6 shows a packet
filtering gateway.
Because we're working at a lower level, supporting new applications either
comes automatically, or is a simple matter of allowing a specific packet type
to pass through the gateway. (Not that the possibility of something
automatically makes it a good idea; opening things up this way might very
well compromise your level of security below what your policy allows.)
There are problems with this method, though. Remember, TCP/IP has
absolutely no means of guaranteeing that the source address is really what it
claims to be. As a result, we have to use layers of packet filters in order to
localize the traffic. We can't get all the way down to the actual host, but with
two layers of packet filters, we can differentiate between a packet that came
from the Internet and one that came from our internal network. We can
identify which network the packet came from with certainty, but we can't get
more specific than that.
Some Words of Caution:-
The business of building firewalls is in the process of becoming a commodity
market. Along with commodity markets come lots of folks who are looking
for a way to make a buck without necessarily knowing what they're doing.
Additionally, vendors compete with each other to try and claim the greatest
security, the easiest to administer, and the least visible to end users. In order to
try to quantify the potential security of firewalls, some organizations have
taken to firewall certifications. The certification of a firewall means nothing
more than the fact that it can be configured in such a way that it can pass a
series of tests. Similarly, claims about meeting or exceeding U.S. Department
of Defense ``Orange Book'' standards, C-2, B-1, and such all simply mean that
an organization was able to configure a machine to pass a series of tests. This
doesn't mean that it was loaded with the vendor's software at the time, or that
the machine was even usable. In fact, one vendor has been claiming their
operating system is ``C-2 Certified'' didn't make mention of the fact that their
operating system only passed the C-2 tests without being connected to any sort
of network devices.
Such gauges as market share, certification, and the like are no guarantees of
security or quality. Taking a little bit of time to talk to some knowledgeable
folks can go a long way in providing you a comfortable level of security
between your private network and the big, bad Internet.
Additionally, it's important to note that many consultants these days have
become much less the advocate of their clients, and more of an extension of
the vendor. Ask any consultants you talk to about their vendor affiliations,
certifications, and whatnot. Ask what difference it makes to them whether you
choose one product over another, and vice versa. And then ask yourself if a
consultant who is certified in technology XYZ is going to provide you with
competing technology ABC, even if ABC best fits your needs.


Security is a very difficult topic. Everyone has a different idea of what ``security'' is, and what levels of risk are acceptable. The key for building a secure network is to define what security means to your organization . Once that has been defined, everything that goes on with the network can be evaluated with respect to that policy. Projects and systems can then be broken down into their components, and it becomes much simpler to decide whether what is proposed will conflict with your security policies and practices. Many people pay great amounts of lip service to security, but do not want to be bothered with it when it gets in their way. It's important to build systems and networks in such a way that the user is not constantly reminded of the security system around him. Users who find security policies and systems too restrictive will find ways around them. It's important to get their feedback to
understand what can be improved, and it's important to let them know why what's been done has been, the sorts of risks that are deemed unacceptable, and what has been done to minimize the organization's exposure to them. Security is everybody's business, and only with everyone's cooperation, an intelligent policy, and consistent practices, will it be achievable.

1 The New Lexicon Webster's Encyclopedic Dictionary of the English
Language. New York: Lexicon.
2 R.T. Morris, 1985. A Weakness in the 4.2BSD Unix TCP/IP Software.
Computing Science Technical Report No. 117, AT&T Bell Laboratories,
Murray Hill, New Jersey.
3 S.M. Bellovin. Security Problems in the TCP/IP Protocol Suite. Computer
Communication Review, Vol. 19, No. 2, pp. 32-48, April 1989.
4 Y. Rekhter, R. Moskowitz, D. Karrenberg, G. de Groot, E. Lear,
``Address Allocation for Private Internets.'' RFC 1918.
5 J.P. Holbrook, J.K. Reynolds. ``Site Security Handbook.'' RFC 1244.
6 M. Curtin, ``Snake Oil Warning Signs: Encryption Software to Avoid.''
USENET <sci.crypt> Frequently Asked Questions File.
7 Shield your computer from internet crime. By Richard Mansfield
8 Internet security by Chris Prossie..
9 Incident Response by KevinMandia.
10 802.7 security by Bruce Potter.
Post: #2
TCP/IP reference model

Example Networks

The Internet

Connection-Oriented Networks: X.25, Frame Relay, and ATM


Wireless LANs: 802:11
Post: #3
i need network security project plz send me
Post: #4
i am pursuing MBA-IT and i have to prepare a reasearch report on network security system
Post: #5
Abstract :
Network security can be described as the effort to create a secure computing platform, designed so that agents (users or programs) cannot perform actions that they are not allowed to perform, but can perform the actions that they are allowed to. Network Security systems insure the integrity of the system by protecting from hackers trying to get into the system and by restricting access within the system to individuals specific needs.
We have dealt with one of the Basic Network Security Tools the Firewalls. It is a combination of hardware and software that secures access to a local network or computer. A firewall guards the local network by analyzing the data leaving and entering, allowing authorized traffic through while keeping unauthorized traffic out.
Firewalls are typically configurable by network administrators so that they can set policy to determine what traffic is deemed safe. A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. Firewalls use one or more of three methods to control traffic flowing in and out of the network: packet filtering, proxy service, and stateful inspection.
Firewalls are customizable (add or remove filters) through IP address, protocols, domain services etc. They protect the network from SMTP session hijacking, denial of service, spam, viruses, e-mail bombs etc. A function that is often combined with a firewall is a proxy server. The proxy server is used to access Web pages by the other computers.
Hence we conclude that Network Security has become a mandatory thing for every network to such an extent that we can’t imagine a world without it in future.
Network is medium for communication. Security has become a mandatory thing for every network .To protect these networks from attacks (that may be internal or external) security must be provided. It can be provided through secure network devices like firewalls.
What is Network Security?
Network security can be described as the effort to create a secure computing platform, designed so that agents (users or programs) cannot perform actions that they are not allowed to perform, but can perform the actions that they are allowed to. Network Security systems insure the integrity of the system by protecting from hackers trying to get into the system and by restricting access within the system to individuals specific needs.
We have dealt with one of the Basic Network Security Tools the Firewalls.
What is a Firewall?
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranet. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
Firewalls make it possible to filter incoming and outgoing traffic that flows through your system. A firewall can use one or more sets of ``rules'' to inspect the network packets as they come in or go out of your network connections and either allows the traffic through or blocks it. The rules of a firewall can inspect one or more characteristics of the packets, including but not limited to the protocol type, the source or destination host address, and the source or destination port.
Firewalls can greatly enhance the security of a host or a network. They can be used to do one or more of the following things:
• To protect and insulate the applications, services and machines of your internal network from unwanted traffic coming in from the public Internet.
• To limit or disable access from hosts of the internal network to services of the public Internet.
• To support network address translation (NAT), which allows your internal network to use private IP addresses and share a single connection to the public Internet (either with a single IP address or by a shared pool of automatically assigned public addresses).
After reading this chapter, you will know:
• How to properly define packet-filtering rules.
• The differences between the firewalls built into FreeBSD.
• How to use and configure the OpenBSD PF firewall.
• How to use and configure IPFILTER.
• How to use and configure IPFW.
Before reading this chapter, you should:
• Understand basic FreeBSD and Internet concepts
Post: #6
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to get information about the topic network security full report ppt and related topic refer the link bellow
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Hey I want network security seminars report
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i need lots of seminars reports on network security from which i have to choose one for me.
Post: #10
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