Mobile Ad Hoc Network Security Threats Computer Science Essay

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This chapter will predominantly focus on the justification of performing a research upon this subject by taking into account the present security threats in the Mobile Ad hoc network. To paraphrase the above sentence, the main task in this chapter is to answer the question what can be done to prevent the attacks so a study on the "Security threats in Mobile Ad hoc network" is a need.

Ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. One main challenge in design of these networks is their vulnerability to security attacks. In this paper, we study the threats an ad hoc network faces and the security goals to be achieved. We identify the new challenges and opportunities posed by this new networking environment and explore new approaches to secure its communication. In particular, we take advantage of the inherent redundancy in ad hoc networks - multiple routes between nodes - to defend routing against denial of service attacks.

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An ad hoc network is a collection of wireless mobile nodes that forms a temporary network without any centralized administration. In such an environment, it may be necessary for one mobile node to enlist other hosts in forwarding a packet to its destination due to the limited transmission range of wireless network interfaces. 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 the direct 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. This idea of Mobile ad hoc network is also called infrastructureless networking, since the mobile nodes in the network dynamically establish routing among themselves to form their own network on the fly [1].

Mobile nodes that are within each other's radio range communicate directly via wireless links, while those that are far apart rely on other nodes to relay messages as routers. Node mobility in an ad hoc network causes frequent changes of the network topology. Figure 1 shows such an example: initially, nodes A and D have a direct link between them. When D moves out of A's radio range, the link is broken. However, the network is still connected, because A can reach D through C, E, and F

E

F

C

D

B

B

A

C

E

F

D

A

(B)

(Figure 1)

Figure 1: Topology change in ad hoc networks: nodes A, B, C, D, E, and F constitute an ad hoc network.

The circle represents the radio range of node A. The network initially has the topology in (a). When node D moves out of the radio range of A, the network topology changes to the one in (b).

Problem Background

Now-a-days, Mobile ad hoc network (MANET) is one of the recent active fields and has

received marvelous attention because of their self-configuration and self-maintenance capabilities [2]. While early research effort assumed a friendly and cooperative environment and focused on problems such as wireless channel access and multihop routing, security has become a primary concern in order to provide protected communication between nodes in a potentially hostile environment. Recent wireless research indicates that the wireless MANET presents a larger security problem than conventional wired and wireless networks.

Although mobile ad hoc networks have several advantages over the traditional wired networks, on the other sides they have a unique set of challenges. Firstly, MANETs face challenges in secure communication. For example the resource constraints on nodes in ad hoc networks limit the cryptographic measures that are used for secure messages. Thus it is susceptible to link attacks ranging from passive eavesdropping to active impersonation, message replay and message distortion. Secondly, mobile nodes without adequate protection are easy to compromise. An attacker can listen, modify and attempt to masquerade all the traffic on the wireless communication channel as one of the legitimate node in the network. Thirdly, static configuration may not be adequate for the dynamically changing topology in terms of security solution. Various attacks like DoS (Denial of Service) can easily be launched and flood the network with spurious routing messages through a malicious node that gives incorrect updating information by pretending to be a legitimate change of routing information. Finally, lack of cooperation and constrained capability is common in wireless MANET which makes anomalies hard to distinguish from normalcy. In general, the wireless MANET is particularly vulnerable due to its fundamental characteristics of open medium, dynamic topology, and absence of central authorities, distribution cooperation and constrained capability [3]

1.2 Related Work

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A number of researches are done on security challenges and solutions in Mobile ad hoc

Network. Zhou and Haas have proposed using threshold cryptography for providing

security to the network [4]. Hubaux et al. have defined a method that is designed to ensure equal participation among members of the ad hoc group, and that gives each node the authority to issue certificates [5]. Kong, et al. [6] have proposed a secure ad hoc routing protocol based on secret sharing; unfortunately, this protocol is based on erroneous assumptions, e.g., that each node cannot impersonate the MAC address of multiple other nodes. Yi et al. also have designed a general framework for secure ad hoc routing [7]. Deng, et al. have focused on the routing security issues in MANETs and have described a solution of 'black hole' problem [3]. Sanzgiri, et al. have proposed Security Threats in Mobile Ad Hoc Networks secure routing protocol ARAN Which is based on certificates and successfully defeats all identified attacks [8].Yang, et al. have identified the security issues related to multihop network connectivity, discussed the challenges to security design, and reviewed the state-of-art security proposals that protect the MANET link- and network-layer operations of delivering packets over the multihop wireless channel [9]. In this paper, the emphasis is given only on the link layer and network layer security issues.

1.3 Research Goals

In this thesis, we focus on the overall security threats and challenges in Mobile ad hoc

networks (MANET). The security issues are analyzed from individual layers namely

application layer, transport layer, network layer, link layer and physical layer. This

modularity extends the clarity and depicts the original scenario in each layer. The

solutions of the current problems are also reported here so that one may get direction.

This study provides a good understanding of the current security challenges and solutions

of the MANETs. In general the following questions are addressed in our thesis:

What are the vulnerabilities and security threats in MANET? Which level is most

vulnerable to attack?

How the security services like confidentiality, integrity and authentication can be

achieved from mobile ad hoc networks? What steps should be taken?

What are the countermeasures? How the security of the entire system is ensured?

What are the potential dangers that may be crucial in future?

1.4 Guidance to work

Network layer, Transport layer and Application layer respectively. The following two tables, precisely Table 1.1[10] summarizes the attacks and Table 1.2 [9] represents the solutions in each layer in MANET.

Table 1.1: Security attacks on each layer in MANET

SL

NO

LAYER

ATTACKS

1

Application

Repudiation, data corruption

2

Transport layer

Session hijacking, SYN flooding

3

Network layer

Wormhole, blackhole, byzantine, flooding, resource consumption, location disclosure attacks.

4

Data link layer

Traffic analysis, monitoring, disruption, MAC (802.11), WEP weakness.

5

Physical layer

Jamming, interceptions, eavesdropping.

Table 1.2: Security solutions for MANETS

SL

NO

LAYER

SECURITY ISSUES

1

Application

Detecting and prevention viruses, worms, malicious codes, and application abuses.

2

Transport layer

Authentication and securing end-to-end or point-to-point communication through data encryption.

3

Network layer

Protecting the ad hoc routing and forwarding protocols

4

Data link layer

Protecting the wireless MAC protocol and providing link layer security support.

5

Physical layer

Preventing signal jamming denial of service attacks.

1.5 Our Work

Security should be taken into account at the early stage of design of basic networking

mechanisms. In our study, we have identified the security threats in each layer and

corresponding countermeasures. The following table summarizes the potential security

attacks and the actions that can be taken to prevent the attacks.

TABLE 1.3 Security threats and counter measures.

Layers

Attacks

Solutions

Application

Layer

Lack of cooperation attacks,

Malicious code attacks (virus, worms, spyware, Trojan horses etc.

Cooperation enforcement (Nuglets, confidant, CORE) mechanisms, Firewalls, IDS etc.

Transport

Layer

Session hijacking attack, SYN flooding attack, TCP ACK storm attack etc.

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Authentication and securing end-to-end or point-to-point communication, use of public cryptography (SSL, TLS, SET, PCT) etc.

Network layer

Routing protocols attacks (e.g. DSR, AODV etc), cache poisoning, table overflow attacks, Wormhole, blackhole, Byzantine, flooding, resource consumption, impersonation, location disclosure attacks etc.

Source authentication and message integrity mechanisms to prevent routing message modification, securing routing protocols (e.g IPsec, ESP, SAR, ARAN) to overcome blackhole, impersonation attacks, packet leashes, SECTOR mechanisms for wormhole attack etc.

Data link

Layer

Traffic analysis, monitoring, disruption MAC (802.11), WEP weakness etc.

No effective mechanism to prevent traffic analysis and monitoring, secure link layer protocol like LLSP, using WSA etc.

Physical

Layer

Jamming , interceptions, eavesdropping

Using spread spectrum mechanisms e.g FHSS, DSSS etc.

1.6 Application field:

MANETs are a new paradigm of wireless wearable devices enabling instantaneous person-to-person, person-to-machine or machine-to-person communications immediately and easily. Possible commercial applications include business associates sharing information during a meeting, students using laptop computers to participate in an interactive lecture, and emergency disaster relief personnel coordinating efforts in natural disasters. In these applications, where a fixed backbone is not available, a readily deployable wireless network is needed. Mobile ad hoc networks are also a good alternative in rural areas or third world countries where basic communication infrastructure is not well established. Another interesting application of mobile ad hoc networks is ubiquitous computing. Intelligent devices are connected with one another via wireless links and are self-organized in such a way that a newly joined node can request service from local servers without any human intervention.

CHAPTER 2 :

Overview / Limitations:

2.1Overview Of Security Services In Mobile Ad Hoc Network:

The ultimate goals of the security solutions for MANETs is to provide security services, such as authentication, confidentiality, integrity, authentication, nonrepudiation, anonymity and availability to mobile users. In order to achieve this goal, the security solution should provide complete protection spanning the entire protocol stack. There is no single mechanism that will provide all the security services in MANETs. The common security services are described below.

2.1.1 Availability

Availability is concerned with the (unauthorized) upholding of resources. A variety of

attacks can result in the loss of or reduction in availability. Some of these attacks are

amenable to automated countermeasures such as authentication and encryption whereas

others require some sort of action to prevent or recover from loss of availability of

elements or services of a distributed system. Availability ensures the survivability of

network services despite of various attacks. For example, on the physical and media

access control layers, an adversary could employ jamming to interfere with

communication on physical channel while on network layer it could disrupt the routing

protocol and continuity of services of the network. Again, in higher levels, an adversary

could bring down high-level services such as key management service, authentication

service [4].

2.1.2 Confidentiality

Confidentiality ensures that certain information is only readable or accessible by the

authorized party. Basically, it protects data from passive attacks. Transmission of

sensitive information such as military information requires confidentiality. Release of

such information to enemies could have devastating consequences e.g. ENIGMA. Routing and packet forwarding information must also remain confidential so that the enemies could never take the advantages of identifying and locating their targets in a battlefield.

With respect to the release of message contents, several levels of protection can be

identified.

2.1.3 Integrity

Integrity guarantees that the authorized parties are only allowed to modify the

information or messages. It also ensures that a message being transmitted is never

corrupted. As with confidentiality, integrity can apply to a stream of messages, a single

message or selected fields within a message. But, the most useful and straightforward

approach is total stream protection. A connection-oriented integrity service, one that

deals with a stream of messages assures that messages are received as sent, with no

duplication, insertion, modification, reordering, or replays. The destruction of data is also

covered under integrity service. Thus it addresses both message stream modification and

denial of service.

2.1.4 Authentication

Authentication ensures that the access and supply of data is done only by the authorized

parties. It is concerned with assuring that a communication is authentic. In the case of a

single message, such as a warning or alarm signal, the function is to assure the recipient

that the message is from the source that it claims to be from. Without authentication, an

adversary could masquerade as a node, thus gaining unauthorized access to resource and

sensitive information and interfering with the operations of the other nodes [4].

2.1.5 Nonrepudiation

Nonrepudiation prevents either sender or receiver from denying a transmitted message.

Thus, when a message is sent, the receiver can prove that the message was in fact sent by

the alleged sender. On the other hand, after sending a message, the sender can prove that

the message was received by the alleged receiver. Nonrepudiation is useful for detection

and isolation of compromised nodes. When node A receives an erroneous message from

node B, nonrepudiation allows A to accuse B using this message and to convince other

nodes that B is compromised.

2.1.6 Scalability

Scalability is not directly related to security but it is very important issue that has a great

impact on security services. An ad hoc network may consist of hundreds or even

thousands of nodes. Security mechanisms should be scalable to handle such a large

network [4]. Otherwise, the newly added node in the network can be compromised by

the attacker and used for gaining unauthorized access of the whole system. It is very easy

to make an island-hopping attack through one rough point in a distributed network.

2.1.7 Summary

In this chapter, common security services are described briefly. Still there is other

security services which also be considered. For example, authorization that is of concern

to certain application. Access control is another one which limits and controls the access

to host systems and applications via communication links. One important point is that

always there is a tradeoff between security services and achieving a good tradeoff among

these services is one fundamental challenge in security design for MANETs.

2.2 Overview Of Security Attacks

The current Mobile ad hoc networks allow for many different types of attacks. Although

the analogous exploits also exist in wired networks but it is easy to fix by infrastructure in

such a network. Current MANETs are basically vulnerable to two different types of

attacks: 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. On the other hand,

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.

Our focus is on vulnerabilities and exposures in the current ad hoc network. We have classified the attacks as modification, impersonation, fabrication, wormhole and lack of cooperation.

2.2.1 Attacks Using Modification

Modification is a type of attack when an unauthorized party not only gains access to but

tampers with an asset. For example a malicious node can redirect the network traffic and

conduct DoS attacks by modifying message fields or by forwarding routing message with

false values. In fig. 2, M is a malicious node which can keep traffic from reaching X by

continuously advertising to B a shorter route to X than the route to X that C advertises

[8]. In this way, malicious nodes can easily cause traffic subversion and denial of

service (DoS) by simply altering protocol fields: such attacks compromise the integrity of

routing computations. Through modification, an attacker can cause network traffic to be

dropped, redirected to a different destination or to a longer route to reach to destination

that causes unnecessary communication delay.

S

A

B

C

D

X

M

Figure 2: Ad hoc network and a malicious node.

Consider the following fig 2.1 Assume a shortest path exists from S to X and, C and X

cannot hear each other, that nodes B and C cannot hear other, and that M is a malicious

node attempting a denial of service attack. Suppose S wishes to communicate with X and

that S has an unexpired route to X in its route cache. S transmits a data packet toward X

with the source route S --> A --> B --> M --> C --> D --> X contained in the packet's

header. When M receives the packet, it can alter the source route in the packet's header,

such as deleting D from the source route. Consequently, when C receives the altered

packet, it attempts to forward the packet to X. Since X cannot hear C, the transmission is

unsuccessful [14].

S

A

B

M

C

D

X

Figure 2.1 : Ad hoc network with Dos attack.

2.2.2Attacks 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.

Spoofing is occurred when a malicious node misrepresents its identity in the network

(such as altering its MAC or IP address in outgoing packets) and alters the target of the

network topology that a benign node can gather. As for example, a spoofing attack allows

forming loops in routing packets which may also result in partitioning network. Here we

have described the scenario in details.

A

B

C

D

E

X

A

B

C

D

E

X

A

B

C

D

E

X

(a)

(b)

(c)

Figure 3 : A sequence of events forming loops by spoofing packets.

In the above fig. 3.3(a), there exists a path between five nodes. A can hear B and D, B can hear A and C, D can hear A and C, and C can hear B, D and E. M can hear A, B, C, and D while E can hear C and next node in the route towards X. A malicious node M can learn about the topology analyzing the discovery packets and then form a routing loop so that no one nodes in his range can reach to the destination X. At first, M changes its MAC address to match A's, moves closer to B and out of the range of A. It sends a message to B that contains a hop count to X which is less than the one sent by C, for example zero. Now B changes its route to the destination, X to go through A as shown in the fig. 3.3(b).Similarly, M again changes its MAC address to match B's, moves closer to C and out of the range of B. Then it sends message to C with the information that the route through B contains hop count to X which is less than E. Now, C changes its route to B which forms a loop as shown in fig. 3.3(c). Thus X is unreachable from the four nodes in the network.

2.2.3 Wormhole Attacks

Wormhole attack is also known as tunneling attack. A tunneling attack is where two or

more nodes may collaborate to encapsulate and exchange messages between them along

existing data routes. This exploit 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. In the fig. 3.4, M1 and M2 are two malicious nodes that

encapsulate data packets and falsified the route lengths.

A

B

M1

S

C

M2

D

FALSELY TUNNELED PATH

encapsulate

decapsulate

.Figure 3.1 Path length spoofed by tunneling.

Suppose node S wishes to form a route to D and initiates route discovery. When M1

receives a RREQ from S, M1 encapsulates the RREQ and tunnels it to M2 through an

existing data route, in this case {M1 --> A --> B --> C --> M2}. When M2 receives the

encapsulated RREQ on to D as if had only traveled {S --> M1 --> M2 --> D}.Neither M1

nor M2 update the packet header. After route discovery, the destination finds two routes

from S of unequal length: one is of 5 and another is of 4. If M2 tunnels the RREP back to

M1, S would falsely consider the path to D via M1 is better than the path to D via A. Thus,tunneling can prevent honest intermediate nodes from correctly incrementing the metric used to measure path lengths.

2.2.4 Lack of Cooperation

Mobile Ad Hoc Networks (MANETs) rely on the cooperation of all the participating

nodes. The more nodes cooperate to transfer traffic, the more powerful a MANET gets.

But one of the different kinds of misbehavior a node may exhibit is selfishness. A

selfishness node wants to preserve own resources while using the services of others and

consuming their 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 and is described briefly in later section.

2.3 Overview of Security Threats in Different Layers:

2.3.1 Security Threats in Physical Layer:

Physical layer security is important for securing MANET as many attacks can take place

in this layer. The physical layer must adapt to rapid changes in link characteristics. The

most common physical layer attacks in MANET are eavesdropping, interference, denial of-service and jamming. The common radio signal in MANET is easy to jam or intercept. Moreover an attacker can overhear or disrupt the service of wireless network physically. An attacker with sufficient transmission power and knowledge of the physical and medium access control layer mechanisms can gain access to the wireless medium. Here we will describe eavesdropping, interference and jamming attacks in brief.

2.3.1(A) Eavesdropping:

Eavesdropping is the reading of messages and conversations by unintended receivers.

The nodes in MANET share a wireless medium and the wireless communication use the

RF spectrum and broadcast by nature which can be easily intercepted with receivers

tuned to the proper frequency. As a result transmitted message can be overheard as well

as fake message can be injected into the network.

2.3.1(B) Interference and Jamming:

Jamming and interference of radio signals causes message to be lost or corrupt. A

powerful transmitter can generate signal that will be strong enough to overwhelm the

target signal and can disrupt communications. Pulse and random noise are the most

common type of signal jamming [10].

2.3.2 Overview Of Security Threats In Link Layer:

The MANET is an open multipoint peer-to-peer network architecture in which the link

layer protocols maintain one-hop connectivity among the neighbors. Many attacks can be

launched in link layer by disrupting the cooperation of the protocols of this layer. Wireless medium access control (MAC) protocols have to coordinate the transmission of the nodes on the common communication or transmission medium.

The first security scheme provided by IEEE 802.11 standards is Wired Equivalent Privacy (WEP). Basically, it was designed to provide security for WLAN.

2.3.3 overview of security threats in network layer

In MANET, the nodes also function as routers that discover and maintain routes to other nodes in the network. Establishing an optimal and efficient route between the communicating parties is the primary concern of the routing protocols of MANET. Any attack in routing phase may disrupt the overall communication and the entire network can be paralyzed. Thus, security in network layer plays an important role in the security of the whole network.

A number of attacks in network layer have been identified and studied in security research. An attacker can absorb network traffic, inject themselves into the path between

the source and destination and thus control the network traffic flow. For example, as shown in the figure 4, a malicious node M can inject itself into the routing path between sender S and receiver R.

S

X

Y

R

(a)

S

X

Y

R

M

(b)

M

Figure 4 : routing attack.

Network layer vulnerabilities fall into two categories: routing attacks and packet forwarding attacks [16]. The family of routing attacks refers to any action of advertising routing updates that does not follow the specifications of the routing protocols. The specific attack behaviors are related to the routing protocol used by the MANET.

2.3.3(A) routing table overflow attack

This attack is basically happens to proactive routing algorithms, which update routing information periodically. To launch routing table overflow attack, the attacker tries to create routes to nonexistent nodes to the authorized nodes present in the network. He/she can simply send excessive route advertisements to overflow the target system's routing table. The goal is to have enough routes so that creation of new routes is prevented or the implementation of routing protocol is overwhelmed.

2.3.3(B)Routing Cache poisoning attack

Routing cache poisoning attack uses the advantage of the promiscuous mode of routing

table updating. This occurs when information stored in routing tables is either deleted,

altered or injected with false information. Suppose a malicious node M wants to poison

routes node to X. M could broadcast spoofed packets with source route to X via M itself,

thus neighboring nodes that overhear the packet may add the route to their route caches[10]

2.3.3( C) Other attacks.

2.3.3(C )i. Wormhole Attack

Wormhole attack is also known as tunneling attack. An attacker creates a tunnel and uses

encapsulation and decapsulation to make a false route between two malicious nodes. In

section 3.4, we have described wormhole attack in detail.

2.3.3(C )ii. Blackhole Attack

The backhole attack is performed in two steps. At first step, the malicious node exploits

the mobile ad hoc routing protocol such as AODV, to advertise itself as having a valid

route to a destination node, even though the route is spurious, with the intention of

intercepting the packets. In second step, the attacker consumes the packets and never

forwards. In an advanced form, the attacker suppresses or modifies packets originating

from some nodes, while leaving the data from the other nodes unaffected. In this way, the

attacker falsified the neighboring nodes that monitor the ongoing packets. In fig. 6.2,

node 1 wants to send data packets to node 4 and initiates the route discovery process. We

assume that node 3 is a malicious node and it claims that it has route to the destination

whenever it receives RREQ packets, and immediately sends the response to node 1. If the

response from the node 3 reaches first to node 1 then node 1 thinks that the route

discovery is complete, ignores all other reply messages and begins to send data packets to

node 3. As a result, all packets through the malicious node is consumed or lost [2]

1

2

6

3

5

4

Figure 5: The black-hole problem

2.3.3(C )iii Byzantine Attack

Byzantine attack can be launched by a single malicious node or a group of nodes that

work in cooperation. A compromised intermediate node works alone or set of

compromised intermediate nodes works in collusion to form attacks. The compromised

nodes may create routing loops, forwarding packets in a long route instead of optimal

one, even may drop packets. This attack degrades the routing performance and also

disrupts the routing services.

2.3.3(C )iv Rushing attack.

In wormhole attack, two colluded attackers form a tunnel to falsify the original route. If

luckily the transmission path is fast enough (e.g. a dedicated channel) then the tunneled

packets can propagate faster than those through a normal multi-hop route, and result in

the rushing attack. Basically, it is another form of denial of service (DoS) attack that can

be launched against all currently proposed on-demand MANET routing protocols such as

ARAN and Ariadne [11].

2.3.3(C )v Resource Consumption Attack

Energy is a critical parameter in the MANET. Battery-powered devices try to conserve

energy by transmitting only when absolutely necessary [2]. The target of resource

consumption attack is to send request of excessive route discovery or unnecessary packets to the victim node in order to consume the battery life. An attacker or

compromised node thus can disrupt the normal functionalities of the MANET. This

attack is also known as sleep deprivation attack.

2.3.3(C )vi Location Disclosure Attack

Location disclosure attack is a part of the information disclosure attack. The malicious

node leaks information regarding the location or the structure of the network and uses the

information for further attack. It gathers the node location information such as a route

map and knows which nodes are situated on the target route.

2.3.4 Security Threats In Transport Layer:

The security issues related to transport layer are authentication, securing end-to-end

communications through data encryption, handling delays, packet loss and so on. The

transport layer protocols in MANET provides end-to-end connection, reliable packet

delivery, flow control, congestion control and clearing of end-to-end connection. Like

TCP protocol in the Internet model, the nodes in a MANET are also vulnerable to the

SYN flooding and session hijacking attacks. In the next sections, threats in transport layer

are discussed in detail.

2.3.4(A) SYN Flooding Attack

The SYN flooding attack is also DoS attack which is performed by creating a large

number of half-opened TCP connections with a target node. TCP connection between

two communicating parties is established through completing three way handshakes which is described in the fig 6. The sender sends a SYN message to the receiver with

SYN with ISNa

ACK ISNa and SYN with ISNb

ACK ISNb

ConnectionFigure 6 : TCP three way handshaking

a randomly generated ISN (Initial Sequence Number). The receiver also generates another ISN and sends a SYN message including the ISN as an acknowledgement of the received SYN message. The sender sends acknowledgement to the receiver. In this way the connection is established between two communicating parties using TCP three way handshakes.

2.3.4(B) Session Hijacking

Session hijacking is a critical error and gives a malicious node the opportunity of

behaving as a legitimate system. All the communications are authenticated only at the

beginning of session setup. The attacker may take the advantage of this and commit

session hijacking attack. At first, he/she spoofs the IP address of target machine and

determines the correct sequence number. After that he performs a DoS attack on the

victim. As a result, the target system becomes unavailable for some time. The attacker

now continues the session with the other system as a legitimate system.

2.3.4( C ) TCP ACK Storm

TCP ACK storm is very simple. But to perform the attack, the attacker launches a TCP

session hijacking attack at the beginning. After that the attacker sends injected session

data as depicted in the figure 7 and node A acknowledges the received data with an ACK

packet to node B. Node B is confused as the packet contains an unexpected sequence number and it tries to resynchronize the TCP session with node A by sending an ACK

packet that contains the intended sequence number. But the steps are followed again and

again and results in TCP ACK storm [10].

Attacker

Attacker

Attacker

2. Acknowledge data with ACK packet

3. Confused B, sends its last ACK to

Try to resynchronize.

2 and 3 repeat over and over

1. Inject data

2.3.5 Security threats in application layer:

Applications need to be designed to handle frequent disconnection and reconnection with

peer applications as well as widely varying delay and packet loss characteristics [12].

Like other layers application layer also vulnerable and attractive layer for the attacker to

attack. Because this layer contains user data that supports many protocols such as SMTP,

HTTP, TELNET and FTP which have many vulnerabilities and access points for

attackers. The main attacks in application layer are malicious code attacks and

repudiation attacks.

2.3.5(A) Malicious Code Attacks

Various malicious codes such as virus, worm, spy-wares and Trojan horse attack both

operating systems and user applications that cause the computer system and network to

slow down or even damaged. An attacker can produce this type of attacks in MANET and

can seek their desire information [10].

2.3.5(B) Repudiation Attacks

The solution that taken to solve authentication or non-repudiation attacks in network

layer or in transport layer is not enough. Because, repudiation refers to a denial of

participation in the communication. Example of repudiation attack on a commercial

system: a selfish person could deny conducting an operation on a credit card purchase or deny any on-line transaction [10].

2.4 Limitations in each layer:

2.4.1 Limitations in Physical layer:

The topology is highly dynamic as nodes frequently leave or join network, and roam in the network on their own will. Again, the communication channel in MANET is bandwidth-constrained and shared among multiple network entities. This channel is also subject to interferences and errors exhibiting volatile characteristics in terms of bandwidth and delay. The attacker may take the opportunity of these volatile characteristics.

2.4.2 Limitations in Link Layer:

The IEEE 802.11 MAC is vulnerable to DoS attacks. To launch the DoS attack, the attacker may exploit the binary exponential backoff scheme. For example, the attacker may corrupt frames easily by adding some bits or ignoring the ongoing transmission. Among the contending nodes, the binary exponential scheme favors the last winner which leads to capture effect. Capture effect means that nodes which are heavily loaded tend to capture the channel by sending data continuously, thereby resulting lightly loaded neighbors to backoff endlessly. Malicious nodes may take the advantage of this capture effect vulnerability. Moreover, it can cause a chain reaction in the upper level protocols using backoff scheme, like TCP window management [10].

The first security scheme provided by IEEE 802.11 standards is Wired Equivalent

Privacy (WEP). Basically, it was designed to provide security for WLAN. But it suffers from many design flaws and some weakness in the way RC4 ciper used in the WEP. It is well known that WEP is vulnerable to message privacy and message integrity attacks and probabilistic cipher key recovery attacks .

Key management is not specified in the WEP protocol. Lack of key management

is a potential exposure for most attacks exploiting manually distributed secrets shared by large populations.

The initialization vector (IV) used in WEP is a 24-bit field which is sent in clear and is a part of the RC4 leads to probabilistic cipher key recovery attack or most commonly known as analytical attack.

2.4.3 Limitations in Network layer:

The network layer is more vulnerable to attacks than any other layer

There are many attacks in MANET that target the particular routing protocols. This is due to developing routing services without considering security issues. Most of the recent research suffers from this problem

The most concerning part in this layer is attacks on routing protocols.

The Ad-hoc On-demand Distance Vector (AODV) routing algorithm is a reactive algorithm that routes data across wireless mesh networks. But in AODV, the attacker may advertise a route with a smaller distance metric than the original distance or advertise a routing update with a large sequence number and invalidate all routing updates from other nodes.

Dynamic Source Routing (DSR) protocol is similar to AODV in that it also forms route on-demand.it is possible to modify the source route listed in the RREQ or RREP packets by the attacker. Deleting a node from the list, switching the order or appending a new node into the list is also the potential dangers in DSR

Authenticated Routing for Ad-hoc Networks (ARAN) is an on-demand routing protocol that detects and protects against malicious actions carried out by third parties and peers in particular ad-hoc environment [8].

ARIADNE is an on-demand secure ad-hoc routing protocol based on DSR that implements highly efficient symmetric cryptography Although ARIADNE is free from a flood of RREQ packets and cache poisoning attack, but it is immune to the wormhole attack and rushing attack.

Specifically, SEAD builds on the DSDV-SQ version of the DSDV (Destination Sequenced Distance Vector) protocol. SEAD does not cope with wormhole attacks.

2.3.4 Limitations in Transport layer:

MANET has a higher channel error rate when compared to wired network. This is due to TCP does not have any mechanism to distinguish the cause of loss i.e. whether it is done by congestion, random error or malicious attacks. On the other hand, UDP is also immune to session hijacking. It is same over UDP as over TCP, except that the attackers need not to be worried about the overhead of managing sequence numbers and other TCP mechanisms since UDP is connectionless protocol.

2.3.5 Limitations in Application layer:

Another fundamental problem in MANET is end-to-end security. Heterogeneous network may suffer from various security threats that may increase packet delivery latency, increase packet loss rate and so on. The main security issues involved in application layers are detecting and preventing viruses, worms, malicious codes and application abuses.

Chapter 3

New Ideas:

Introduction:

Mobile wireless network, capable of autonomous operation operates without base station infrastructure nodes cooperate to provide connectivity operates without centralized administration nodes cooperate to provide services.

Security is an important issue for ad hoc networks, especially for those security-sensitive applications. To secure an ad hoc network, we consider the following attributes: availability, confidentiality, integrity, authentication, and non repudiation.

There are quite a number of uses for mobile ad-hoc networks. For example, the military can track an enemy tank as it moves through the geographic area covered by the network Your local community can use an ad-hoc network to detect your car moving though an intersection, checking the speed and direction of the car. In an environmental network, you can find out the temperature, atmospheric pressure, amount of sunlight, and the relative humidity at a number of locations.

The whole life-cycle of ad-hoc networks could be categorized into the first, second, and the third generation ad-hoc networks systems. Present ad-hoc networks systems are considered the third generation. One of the main concerns in the Mobile Ad hoc Network is Security. Unfortunately all of the widely used ad hoc routing protocols have no security considerations and trust all the participants to correctly forward routing and data traffic. This assumption can prove to be disastrous for an ad hoc network that relies on nodes for packet forwarding. Simulations have shown that if 10%-40% of the nodes that participate in an ad hoc network perform malicious operations, then the average throughput degradation reaches 16%-32% [13]. Earlier surveys and review papers presenting comparisons of ad hoc routing protocols completely ignored security problems [14, 15, and 16]. This paper presents a survey of the solutions that address the problem of secure and robust routing in mobile ad hoc networks.