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The nature of attacks is of two
types’ active attacks and passive attacks. Active attack is an attack when
misbehaving node has to bear some energy costs in order to perform the threat. These
attacks results unauthorised state changes in the network such as denial of
service, modification of packets, and the like. These attacks are generally
launched by users or nodes with authorisation to operate within the network. While
passive attacks are mainly due to lack of cooperation with the purpose of
saving energy selfishly. Nodes that perform active attacks with the aim of
damaging other nodes by causing network outage are considered as malicious while
nodes that make passive attacks with the aim of saving battery life for their
own communications are considered to be selfish.

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4.1 Wormhole

Wormhole attack is also called as
tunnelling attack. A tunnelling attack is where two or more nodes may collaborate
to encapsulate and exchange messages between them along existing data routes.
This exploitation gives the opportunity to a node or nodes to short-circuit the
normal flow of messages creating a virtual vertex cut in the network that is
controlled by the two colluding attackers.

4.2 Attacks
Using Impersonation

As there is no authentication of
data packets in current ad hoc network, a malicious node can launch many
attacks in a network by masquerading as another node i.e. spoofing. Due to a
malicious node misrepresents its identity in the network (such as altering its
MAC or IP address in outgoing packets) and alter the target of the network topology.

4.3 Lack of

Mobile Ad Hoc Networks (MANETs)
rely on the cooperation of all the participating nodes. The more powerful a
MANET gets as the more nodes cooperate to transfer traffic. But one of the
different kinds of misbehaviour a node may exhibit is selfishness. A
selfishness node uses the resources of other nodes while preserving own
resources. This can endanger the correct network operation by simply not
participating to the operation or by not executing the packet forwarding. This
attack is also known as the black hole attack.

4.4 Attacks
through Fabrication

In Fabrication an unauthorized party
not only gains the access but also inserts counterfeit objects into the system.
In MANET, fabrication is used to refer the attacks performed by generating
false routing messages. Such kind of attacks can be difficult to verify as they
come as valid constructs, especially in the case of fabricated error messages
that claim a neighbour cannot be contacted.

Security Attacks on each layer in


Layer                          Attacks

Application layer                 Repudiation, data corruption

Transport layer                    Session hijacking, SYN                                       flooding

Network layer                       Wormhole, black hole,
Byzantine, flooding,

consumption location disclosure attacks

Data link layer                     Traffic analysis,
monitoring, disruption MAC (802.11),

WEP weakness

Physical layer       Jamming, interceptions, eavesdropping

Table – 2

Security Issues for MANET

Layer                                    Security

Application layer                 Detecting and preventing

malicious codes and application abuses

Transport layer                    Authentication and                                             securing
end to-end or                                        point-to-point                                                       communication

through data encryption

Network layer                       Protecting the ad hoc  forwarding protocols

Data link layer                     Protecting the wireless MAC protocol
and providing link layer

security support

Physical layer                       Preventing signal jamming denial-of-service