SECURE MEASURES FOR THE VULNERABILITIES IN MAODV

Transcription

1 ECURE EAURE OR THE VULNERABILITIE IN AODV r. A. Amuthan Associate Professor Department of Computer cience & Engineering Pondicherry Engineering College P. Bharathi P cholar Department of Computer cience & Engineering Pondicherry Engineering College bharathi.rgcet@gmail.com Abstract obile Adhoc NETworks (ANETs) is a highly challenged network environment due to its special characteristics such as decentralization, dynamic topology and neighbor based routing. ost important application for ad-hoc networks is group oriented in nature and can therefore benefit from a multicast communication services. ost of the multicast routing protocols assume trusted, non-adversarial environment and do not take security issues into the account. The security issue of ANETs in group communication is more challenging because of multiple senders and multiple receivers. ANET is vulnerable to several types of security attack [2] and the focus of earlier research is only on unicast applications [3]. In this paper, we analyzed the security of AODV (ulticast Ad hoc On Demand Distance Vector protocol), a wellknown multicast routing protocol and identified some routing attacks like black hole, wormhole and flooding. AODV is a multicast routing protocol for ad-hoc networks that dynamically constructs a shared multicast tree which connects the group members, possibly through some non-member nodes which may or may not be on the tree in order to multicast data to all group members. We proposed a trust based approach in which each node maintains a log of success and failure rate of packet transmissions which are then used to determine the trust values there by helping in the mitigation black hole and worm hole attacks. 1. Introduction In this paper we provide a brief description of the AODV protocol. We discuss the various flaws in the security mechanism that makes it exploited by the malicious nodes to stage a black hole attack, worm hole attack and flooding attack in the network. 1.1 Overview of AODV AODV [1] is a multicast operation of AODV(Adhoc On-demand Distance Vector) Routing protocol. It shares many similarities and packet formats with AODV. 1.2 eatures of AODV Routing scheme reactive routing protocol which discovers routes on demand. Initialization approach receiver node wishing to join into the group by flooding the join request message to find out a route to the multicast group. ulticast topology shared tree multicast routes are constructed for the members of the multicast group. aintenance approach reactive hard state approach for efficient group maintenance. 1.3 Control Packets RREQ (route request) this packet is broadcasted by a node when it wishes to join into the group or find a route to the multicast group. There are two types of RREQ which depends on the join flag set in the RREQ. Join flag is set when it wishes to join into group and it is unset when it just wants to find a route to the multicast group. RREP (route reply) this packet is generated in response to the RREQ initiated by the node. When a node receives a RREQ it first checks whether join flag is set. If it is set, only the intended group member can reply to the RREQ. Otherwise any node with a current route to the multicast group can reply. ACT (multicast activation) when a node receives a RREQ it is likely to receive more than one reply. After waiting RREP wait time milliseconds, the node selects 601

2 its link to the multicast tree based on the two fields highest sequence number and smallest hop count. If the node receives more than one RREP, it selects the one with the smallest hop count (i.e) shortest distance to a member of the multicast tree. RPH (group hello) each multicast group has a group leader. When a node wishes to find a multicast group, it then broadcasts RREQ message and then waits for a reply. In some number of attempts, it doesn t receive a reply it may assume itself as a group leader and initializes its sequence number to one. Once it becomes the group leader it then broadcast the group hello message periodically. 1.4 Routing table Each node running in AODV must maintain two tables. They are ulticast routing table (multicast group address and multicast group leader ip address, multicast group sequence number, hop count to multicast group leader, next hop) roup leader table (multicast group address and multicast group leader IP address) 1.5 Route Discovery and Link Activation igure 1, 2 and 3 describes the process of route discover and link activation in AODV. When a node either wants to connect with the multicast group or find a route to the multicast group, the node broadcasts a RREQ message. or join requests, a reply is sent when the RREQ reaches a node that is already a member of the multicast tree, and the node s record of the multicast group sequence number is at least as great as that contained in the RREQ. or non-join requests, any node with a present route to the multicast tree may respond to the RREQ. The route to the multicast tree is constructed by unicasting a RREP back to the source of the RREQ. Tree Pruning: If a forwarded node, which is not a member of the multicast group, becomes a leaf node, it prunes itself from the tree. It is accomplished by setting Prune flag in the ACT message and sends it to the next hop. Link Repair: Each node on the multicast tree always monitors the status of the links with its immediate neighbours. When a link breakage is detected, the node downstream of the break (i.e., the node that is further from the multicast group leader) is responsible for repairing the broken link. -roup leader -orwarding node -ember node -ource node igure 1. ource initiates RREQ to the roup() 1.6 ulticast tree maintenance ulticast tree maintenance mainly involves three operations (i) Tree Pruning, (ii) Link Repair, and (iii) Partition erging. 602

3 three trust based reactive routing protocols (AODV, TORA and DR) has been evaluated in an attacked environment. In [6] defines the trust value in routing protocols and also it describes the five trust based route strategies to select secure route to a destination. In [7], a fidelity table is maintained for each node wherein every neighbor will be assigned a fidelity level which serves as a measure of reliability of that node. In [8], a trust value will be calculated for each node in the network which represents the trustworthiness of its neighbor nodes. The trust value will be updated based on the behavior that the node has with its neighbors. igure 2. ource receives reply igure 3. ource() accepts reply and sends ACT to the neighbour hop node who has the best route Partition erging: Nodes in one partition of the multicast tree will discover another partition when they receive roup Hello packets from the group leader of another partition. These two partitions should be merged to improve the group connectivity. 2. Related Work In [4], the existing AODV routing protocol has been modified to find a secure route to the destination. This mechanism equally emphasis both on the route trust and node trust. In [5] this paper the performance of the 3. Preliminaries and flaws in AODV The major drawback of the AODV protocol is the lack of security mechanisms to ensure that the packets have reached the destination. There is no acknowledgement procedure that is present and hence no delivery validation. A malicious node is capable of bringing about the following type of attacks. Impersonation: A node can impersonate another node by sending a RREQ with its address as the originating address. purious routes: A node can change the hop count information of advertise that it has the shortest route to the destination by sending in a RREP. Denial Of ervice: A node that is in the radio range of other distant nodes can repeatedly put down RREQ s and not forward them thus leading to failure in path discovery. looding: A node can unnecessarily keep flooding the network with RREQ s thereby powering down a sizeable portion of the network. Altering DN: A node can alter its destination sequence number to a node by just sending two or more RREQ packets. Black Hole: A node can announce that which has a fresh enough route to the destination without checking its routing table, receive the data packets from the source and retain them without further forwarding. 4. ATTACK IN AODV 4.1 BLACKHOLE ATTACK When a node either wants to join a multicast group or find a route to a multicast group, it broadcasts a RREQ message. In this attack, a malicious node replies to the RREQ message with the goal of deceiving the node that it has found the best route to the multicast group. 603

4 P.Bharathi,A.Amuthan, Int. J. Comp. Tech. Appl., Vol 2 (3), A igure 6. ince the attacker gives the best route to which establish the link with it. igure 4. ource() initiates RREQ to the group() 4.2 Wormhole Attack In this attack, a pair of attackers, trace packets at one location and replay them at another location using a private high speed network. The wormhole particularly vulnerable to many ad-hoc routing protocols such as on-demand routing protocols. A igure 5. receives reply from the attacker node and other nodes in ANET Consider a node A that wants to join the multicast group. A Broadcast a RREQ packet with the multicast group address as the destination address and with the J (Join) flag set. Only nodes on the multicast tree be eligible to send a reply (RREP) to this request. However, a malicious node can respond to the RREQ packet with a RREP even if it is not on the multicast tree. A RREP packet includes the replying node s view of the group sequence number. ince A is likely to receive RREPs from multiple nodes, in order to increase the chances of the route to being selected as the best route to the multicast group, can fabricate the sequence number field in its RREP. In this protocol a malicious node at one part of the network and hears the RREQ packet. It tunnels it to its peer attacker at a distant location near the destination. The second party then rebroadcasts the RREQ. The neighbors of the second colluding party receive the RREQ and drop any further legitimate requests that may arrive later on legitimate multihop paths. This achieves that the routes between the source and the destination go through the two colluding nodes that will be said to have formed a wormhole between them. This prevents nodes from determining legitimate paths that are more than two hops away. 5. Trust Based olution or Both Black Hole Attack And Wormhole Attack This solution guarantees that multicast data is delivered from the source to the members of the multicast group, even in the presence of attackers and it also ensures that only authorized nodes perform certain operations (only tree nodes can perform tree operations and only group nodes can connect to the corresponding multicast tree). This solution is also capable of mitigating attacks that tries to prevent a node from establishing a route to the multicast tree both in route request and route reply. 604

5 A new parameter trust value named TV is used to choose the best path which ensures trustworthiness of the path by calculating the trust value of the neighbor nodes which is later stored in a trust table. Each time a node sends a RREQ either when it finds out that it should be a part of a multicast group, and it is not already a member of that group, or when it has a message to send to the multicast group but does not have a route to that group, an immediate node after receiving a RREQ packet updates its path in the routing table and add the trust value TV of its link and forward it to the next node. An entity gathers information about the data and control packets of its neighboring node and overhears data whether a packet of control message is dumped and not retransmitted. Based on this, every node is set to maintain some values in a table for its neighboring node. The trust level can be calculated based on the events recorded in table. Count RREQ RREP ACT roup Hello Data uccess q rs q ps q mt g gh q da ail q rf q pf q mf g gf q df Table 1. Trust level The trust factor can be calculated as follows Qr = ( q rs - q rf ) / ( q rs +q rf ) Q p = ( q ps - q pf ) / ( q ps + q pf ) Q m = ( q mt - q mf ) / ( q mt + q mf ) Q g = ( q gh - q gf ) / ( q gh + q gf ) Q d = ( q da - q df ) / ( q da +q df ) Now the values of Qr, Qp, Q m, Q g and Q d are normalized in -1 to 1. These factors represent the reliability of the particular event which varies in the range of unimportant to most important. Negative values for trust can take place as a result of more failures than success for an event. Hence a trust value of -1, represents complete dis-trustness, 0 implies noncontributing event and 1 means absolute trust in a particular event. The trust values are then assigned weights to determine the aggregate trust level for another node. The trust values can be calculated as Ty J R igure 7. odified RREQ ormat HC-Hop Count TV-Trust Value R-Rerserved T-Type J-Join lag R-Repair lag -roup Leader lag TV = W(RREQ) * Qr + W(RREP)* Q p + W(ACT)* Q m + W(RPH) * Q g + W(DATA)* Q d Where function W is the weight value of corresponding packet category. These values are dynamically updated based on the successful delivery of a packet or receiving an error message. Upon receiving the rout replies, best path will be chosen by the source depending on the average trust level TV (avg) value of the entire path which can be calculated as TV (avg) = TV / Hop count TV Res BROADCAT ID DET ADDR DET_EQR OURCE_ADDR OURCE_EQ HC Every source will maintain a table (Average trust value table) which contains destination host, next hop and average trust level for the existing paths. These values are updated based on the received RREP messages. This solution prevents malicious nodes from being a part of a multicast tree or joins a multicast tree. Each node forwards RREQ/RREP only when the node from which RREQ/RREP is received a must be a trusted node. 6. imulations The performance of the network depends on the number of receivers, senders and attackers. We made our simulation on the assertion that there are 2 attackers in the initial simulation time and gradually increased to 8 attackers as the simulation time progresses in the network and they are selected randomly. To simply the scenario, we assume that the attacker node successfully launches the rushing attack and as a result of it, they start discarding all the data packets. 605

6 We perform our simulation using ns 2.26 simulator by making some modification in AODV implementation to evaluate the performance of our proposed approach. The simulation settings are as follows. Network ize Total Number Of 40 Nodes No Of alicious 2-8 nodes Packet ize 1000 Traffic Type CBR 6.2 Performance etrics Packet Delivery Ratio: The ratio of the number of data packets delivered to the destination to the number of data packets generated by the sources. igure.4 and 5 shows the variation of packet delivery ratio of AODV in presence of attackers, in the absence of attackers and our solution in the presence of attackers. The PDR obtained using AODV without attackers is almost same as our solution in the presence of attackers. We observe a drop in PDR when the numbers of attackers are increased from 2 to 8. igure 9. Wormhole Attack 7. Conclusion ecurity is one of the critical issues in multicast routing protocol. In this paper we analyzed the vulnerabilities in AODV routing protocol and proposed a trust based solution to defend against the security attacks like black hole and wormhole. We proposed solution for the multicast routing protocol AODV that works well even in the presence of attackers. Our future work is to adopt other popular multicast routing protocol, propose secure measures to defend against the routing attack which then creates secure communication among the multicast group. 8. References [1] Osamah. Badarneh and ichel Kadoch, ulticast Routing Protocols in obile Ad Hoc Networks: A Comparative urvey and Taxonomy, EURAIP Journal on Wireless Communications and Networking, Volume 2009 (2009), Article ID , 42 pages. [2] Hoang Lan Nguyen, UyenTrang Nguyen, "tudy of Different Types of Attacks on ulticast in obile Ad Hoc Networks," icniconsmcl, pp.149, International Conference on Networking, International Conference on ystems and International Conference on obile Communications and Learning Technologies (ICNICONCL'06), [3] N.hanthi, Dr.Lganesan And Dr.K.Ramar, tudy Of Different Attacks On ulticast obile Ad Hoc Network, Journal of Theoretical and Applied Information Technology, 45-51, [4] A.enaka Pushpa, Trust Based ecure Routing in AODV Routing Protocol, IEEE, pp: 1 6, igure 8. Black hole Attack [5] Asad Amir Pirzada, Chris cdonald, and Amitava Datta, ember, Performance Comparison of Trust-Based Reactive Routing Protocols, IEEE Transactions On obile Computing, VOL. 5, NO. 6,pp: , JUNE

7 [6] uo Wei1 Xiong Zhongwei2 Li Zhitang1, Dynamic Trust Evaluation Based Routing odel for Ad Hoc Networks, IEEE, pp: , [7] Latha Tamilselvan, Prevention of Co-operative Black Hole Attack in ANET, JOURNAL O NETWORK, VOL. 3, NO. 5, pp: 13-20, AY [8] N.Bhalaji and Dr.A.hanmugam, Association Between Nodes To Combat Blackhole Attack In Dsr Based anet, pp: 1 5,