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2. Introduction

As the world has become a global
village due to the availability of instant information and communication within
no time. The more advancement in communication devices like cell phones,
handheld digital devices, laptops, personal digital assistants and wearable
computers bringing a revolutionary changes in our information society.
Computing era is changing from one computer for one person to Ubiquitous
Computing age, in which a single user can utilize several electronic platforms
through which he can access all the required information whenever and wherever
needed.

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Wireless networks are one of the
best solutions for these ubiquitous devices to interconnect with each other. As
a consequence the wireless communication has been experiencing exponential
growth in the past decade.

Now we see, all around us these
wireless networks in homes, in office, in platform and everywhere. By using
wireless networks mobile users can use their cellular phone to check e-mail,
browse internet, gets daily updates according to his/her needs. Travellers with
portable computer can surf the internet from the airports, railway stations and
other public locations; tourists can use Global Positioning System and much
more.

There are two basic system models
which provide wireless communications.

One is fixed backbone wireless
system which consists of large number of mobiles nodes and relatively fewer,
but more powerful, fixed nodes. These fixed nodes are hard wired using
landlines. The communication between a fixed node and a mobile node occurs via
the wireless medium. This required a fixed and permanent infrastructure. On the
other hand, the second type is Mobile ad hoc network (MANET) which proposed to
setup a network at required time; however, the transmission range of each
low-power node is limited to each other’s proximity, and out-of-range nodes are
routed through intermediate nodes.

 

A MANET is thought to be a
collection of wireless mobile nodes that are capable of communicating with each
other without the use of any prior network infrastructure or central
administration. The mobile hosts are not restricted to any centralized control.
Although this offers unrestricted mobility and connectivity to the users,

The manageability of network lies
on nodes that form the network. As the range area of wireless network is
limited due to which multiple host may needed for one node to exchange data
with another across the network.

In this kind of network, each mobile
node operates not only as a host but also as a router, forwarding packets for
other mobile nodes in the network that may not be within direct wireless
transmission range of each other.

Each node participates in an ad
hoc routing protocol that allows it to discover multihop paths through the
network to any other node.

The MANET is also called
infrastructure less networking, since the mobile nodes in the network
dynamically establish routing among themselves to form their own network on the
fly.

It is formed instantaneously, and
uses multihop routing to transmit information.

MANET is an adequate way of
establishing communication in such type of situation where geographical or terrestrial
constraints demands a totally distributed network system without any fixed base
station, such as battlefields, military applications, and other emergency and
disaster situations.

A futuristic application of MANET
is sensor network which will consist of several thousand small low-powered
nodes with sensing capabilities.

Recent wireless research
indicates that the wireless MANET presents a larger security problem than
conventional wired and wireless networks. While most of the underlying features
make MANETs useful and popular.

First, all signals moves through
bandwidth-constrained wireless links, which makes it more prone to physical
security threats. Possible link attacks range from passive eavesdropping to active
interference. Mobile nodes without adequate protection are easy to compromise,
capture and hijack. An attacker can listen to and modify all the traffic on the
wireless communication channel, and may attempt to masquerade as one of the
participants. Authentication based on public key cryptography and certification
authorities may be difficult to accomplish in a MANET due to the absence of any
central support infrastructure.

Second, mobile nodes are roaming independently
and are able to move in any direction. Therefore, any security solution with a
static configuration would not be adequate for the dynamically changing
topology. In most routing protocols for a MANET, nodes exchange information about
the topology of the network so that routes can be established between a source and
a destination. All messages are transmitted over the air; any intruder can
maliciously give incorrect updating information by pretending to be a
legitimate change of routing information. For instance, denial of service (DoS)
can easily be launched if a malicious node floods the network with spurious
routing messages. The other nodes may unknowingly propagate the messages.

Third, decentralized decision making in the MANET
relies on the cooperative participation of all nodes. The malicious node used
to modify the traffic by traversing it by refusing cooperation to break the
cooperative algorithms. This causes of centralized intrusion detection schemes
to fail.

Finally, as most of all or some of all MANET
may rely on batteries or the other exhaustible means of their energy. By
forcing a node to replay packets to exhaust its energy, an attacker could
create a new type of DoS attack easily. Frequent disconnection is common in wireless
MANETs, Due to the limited network capacity and battery power of wireless nodes,
which makes anomalies hard to distinguish from normalcy. In general, the
wireless MANET is specifically vulnerable due to its fundamental
characteristics of dynamic topology, open medium, and absence of central
authorities, constrained capability, and distributed cooperation. Existing
security solutions for wired networks cannot be applied directly in wireless
MANETs.

 

 

 

 

 

3. Attacks on
MANET

 

To securing a MANETs is not so
much different from other networks: most typically integrity, confidentiality,
availability, authentication, and non-repudiation.

Integrity means that the
information is not modified or corrupted by unauthorized users or by the
environment.

Confidentiality only authorized
people or systems can have an access or execute protected data or programs. The
sensitivity of information in MANETs may decay much more rapidly than in other
information. For example, yesterday’s troop location will typically be less
sensitive than today’s.

Availability
refers
to the ability of the network to provide services as required. Denials of
Service (DoS) attacks have become one of the most worrying problems for network
managers. In a military environment, a successful DoS attack is extremely
dangerous, and the engineering of such attacks is a valid modern war-goal.

 Authentication
is the verification of claims about the identity of a source of
information. And lastly,

Non-repudiation ensures that
committed actions cannot be denied. In MANETs security goals of a system can
change in different modes (e.g. peace time, transition to war, and war time
of a military network).

The characteristics of MANETs
make them susceptible to many new attacks. At the top level attacks can be
classified according to network protocol stacks.

 Here are some examples in a table of
attacks at different layers. Some attacks could occur in any layer of the
network protocol stack, e.g. jamming at physical layer, hello flood at network
layer, and SYN flood at transport layer are all DoS attacks. As new routing protocols
introduce new forms of attacks on MANETs, we mainly focus on network layer
attacks in this chapter.

Layer                    Attacks

Application           Layer data corruption, viruses and
worms

Transport Layer   TCP/UDP SYN flood

Network Layer     hello flood, black hole

Data Link Layer monitoring, traffic analysis

Physical Layer     eavesdropping,
active interference

Table 1 Some Attacks on
the Protocol Stack

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