March 2015 A New Approach To Detect, Filter And Trace The DDoS Attack
Proceedings of the UGC Sponsored National Conference on Advanced Networking and Applications,27th March 2015A New Approach to Detect, Filter And Trace theDDoS AttackS.Gomathi,M.Phil Research scholar, Department of Computer Science, Government Arts College, Udumalpet-642126.E-mail id: gomathipriya1988@gmail.comDr.E.Karthikeyan M.Sc., M.Phil., Ph.D.,Head & Assistant Professor,Department of Computer Science,Government Arts College, Udumalpet-642126.E-mail id: e ------------------------------------------With the tremendous growth of network-based services and users of the Internet, it is important to keep the data andtransactions in the internet more secure. Since the volume of sensitive and valuable information passing over theInternet is growing very large, the security attacks like Phishing, Spoofing, Flooding, Virus, and Spam areincreasing. The Internet attackers can forge the source address of IP packets to both maintain their anonymity andredirect the blame for attacks. These spoofing packets are often part of some malicious activity, such as a DDoSattack. To thwart DDoS attacks, researchers have taken two distinct approaches: packet filtering and packet tracing.Packet filtering mechanism defines to detect and filter the attacked packet and Packet tracing mechanism defines todetect and trace the source, block the attacked traffic. In the proposed work, combining these two mechanisms toeffectively detect, filter and also trace the DDoS attack.Keywords: DDoS attack, Internet,IP spoofing, packet filtering, packet --------------------------------- ---------resources against the large, sophisticated sites. The attackers1. IntroductionToday, the Internet is an essential part of our in DDoS attacks always modify the source addresses in theeveryday life and many important and crucial services like attack packets to hide their identity, and making it difficultbanking, shopping, transport, health, and communication to distinguish such packets from those sent by legitimateare partly or completely dependent on the Internet. As the users. This idea, called IP address spoofing has been used inInternet was originally designed for openness and scalability major DDoS attacks in the recent past.without much concern for security. Unfortunately, it is notpossible to reliably determine the source of received IP 2. IP Spoofing overviewpackets, as the protocol does not provide authentication ofthe packet based on the source address field, which can beThe basic protocol for sending data over theeasily faked (IP spoofing). Furthermore the Internet routing Internet network and many other computer networks is theinfrastructure also does not keep information about Internet Protocol ("IP"). IP spoofing or Internet protocolforwarded packets. Malicious users can exploit these design address spoofing is the method of creating an Internetweaknesses of the internet to wreak havoc in its operation. protocol packet or IP packet using a fake IP address that isIncidents of disruptive activities which have raised the most impersonating a legal and legitimate IP address. IP spoofingconcern in recent years are the denial-of-service (DoS) is a method of attacking a network in order to gainattacks [1] whose sole purpose is to reduce or eliminate the unauthorized access. The attack is based on the fact thatavailability of a service provided over the Internet, to its Internet communication between distant computers islegitimate users. This is achieved either by exploiting the routinely handled by routers which find the best route byvulnerabilities in the software, network protocols, or examining the destination address, but generally ignore theoperation systems, or by exhausting the consumable origination address. The origination address is only used byresources such as the bandwidth, computational time and the destination machine when it responds back to the sourcememory of the victim. The first kind of attacks can be [2].avoided by patching-up vulnerable software and updatingthe host systems from time to time. In comparison, thesecond kind of DoS attacks is much more difficult todefend. This works by sending a large number of packets tothe target, so that some critical resources of the victim areexhausted and the victim can no longer communicate withother users.In the distributed form of DoS attacks (calledDDoS), the attacker first takes control of a large number ofvulnerable hosts on the internet, and then uses them tosimultaneously send a huge flood of packets to the victim,exhausting all of its resources. There are a large number ofFig.1. Intruder in communicationexploitable machines on the internet, which have weaksecurity measures, for attackers to launch DDoS attacks, soIn a spoofing attack, the intruder sends messages tothat such attacks can be executed by an attacker with limited a computer indicating that the message has come from aSpecial Issue Published in Int. Jnl. Of Advanced Networking and Applications (IJANA)Page 71
Proceedings of the UGC Sponsored National Conference on Advanced Networking and Applications,27th March 2015trusted system. To be successful, the intruder must firstdetermine the IP address of a trusted system, and thenmodify the packet headers to that it appears that the packetsare coming from the trusted system. These includeobscuring the true source of the attack, implicating anothersite as the attack origin, pretending to be a trusted host,hijacking or intercepting network traffic, or causing repliesto target another system. Spoofing of network traffic canoccur at many layers. Examples include network layerspoofing (e.g. Ethernet MAC spoofing), non-IP transportlayer spoofing (e.g. IPX, NetBEUI), as well as session andapplication layer spoofing (e.g. email spoofing). All of thesehave significant security concerns.2.1 IP Address Spoofing AttacksBlind spoofing- This attack may take place from outsidewhere sequence and acknowledgement numbers areunreachable. Attackers usually send several packets to thetarget machine in order to sample sequence numbers, whichis doable in older days. Using the spoofing to interfere witha connection (or creating one), that does not send packetsalong your cable [3].Non-Blind spoofing- This type of attack takes place whenthe attacker is on the same subnet as the victim. Thesequence and acknowledgement numbers can be sniffed,eliminating the potential difficulty of calculating themaccurately. The biggest threat of spoofing in this instancewould be session hijacking. This is accomplished bycorrupting the data stream of an established connection,then re-establishing it based on correct sequence andacknowledgement numbers with the attack machine. Usingthis technique, an attacker could effectively bypass anyauthentication measures taken place to build the connection[3].Man in the Middle Attack- This is also called connectionhijacking. In these attacks, a malicious party intercepts alegitimate communication between two hosts to controls theflow of communication and to eliminate or alter theinformation sent by one of the original participants withouttheir knowledge [3].Denial-Of-Service- To make tracing and stopping the DoSis difficult when the attacker spoof source IP addresses.When multiple compromised hosts are participating in theattack, all sending spoofed traffic; it is very challenging toquickly block the traffic. IP spoofing is almost always usedin denial of service attacks (DoS), in which attackers areconcerned with consuming bandwidth and resources byflooding the target with as many packets as possible in ashort amount of time [3].3. Related WorksMany approaches against IP spoofing have beenproposed by researchers recently. Ingress filtering is atechnique used to make sure that incoming packets areactually from the networks that they claim to be from [4].Egress filtering is the practice of monitoring andpotentially restricting the flow of information outboundfrom one network to another. Typically it is informationfrom a private TCP/IP computer network to the Internet thatis controlled [4].Next approach for filtering spoofed IP packets,called Spoofing Prevention Method (SPM). The methodenables routers closer to the destination of a packet to verifythe authenticity of the source address of the packet. Thisstands in contrast to standard ingress filtering which iseffective mostly at routers next to the source and isineffective otherwise. In the proposed method a uniquetemporal key is associated with each ordered pair of sourcedestination networks (AS’s, autonomous systems). Eachpacket leaving a source network S is tagged with the keyK(S;D), associated with (S;D), where D is the destinationnetwork. Upon arrival at the destination network the key isverified and removed. Thus the method verifies theauthenticity of packets carrying the address s which belongsto network S. An efficient implementation of the method,ensuring not to overload the routers, is presented [5]. Themajor benefits of the method are the strong incentive itprovides to network operators to implement it, and the factthat the method lends itself to stepwise deployment, since itbenefits networks deploying the method even if it isimplemented only on parts of the Internet. These twoproperties, not shared by alternative approaches, make it anattractive and viable solution to the packet spoofingproblem.SAVE (Source Address Validity Enforcement)protocol when employed enforces all IP packets to carrycorrect source address. Source Address ValidityEnforcement protocol (SAVE) is based on the building anincoming table that consists of association of each incominginterface of the router with different valid source addressblock. If such tables are deployed at many routers, choicesof spoofing addresses reduced to great extent. Every routerhas a forwarding table that indicates the outgoing interfacefor a given destination. SAVE suggests that there must bean incoming interface for a source address. Suggesting allpackets from specified address space can be reach todestination indicated in incoming table of the router [6].In Hop-count filtering, an attacker can forge anyfield in the IP header, he cannot falsify the number of hopsan IP packet takes to reach its destination. An Internetserver can easily infer the hop-count information from theTime-to-Live (TTL) field of the IP header. Using a mappingbetween IP addresses and their hop-counts, the server candistinguish spoofed IP packets from legitimate ones. Basedon this observation, we present a novel filtering technique,called Hop-Count Filtering (HCF)—which builds anaccurate IP-to-hop-count (IP2HC) mapping table—to detectand discard spoofed IP packets. HCF is easy to deploy, as itdoes not require any support from the underlying network[7].In Updated Hop Count Filtering, the victim candetect and discard the spoofed packets and forward theinformation to each neighbor routers. It is updated versionof hop count filtering.The probabilistic packet marking (PPM) algorithmwas originally suggested by Burch and Cheswick [8] andwas carefully designed and implemented by Savage et al.[1] to solve the IP trace back problem. It is a used todiscover the Internet map or an attack graph during adistributed denial-of-service attack. The PPM algorithmSpecial Issue Published in Int. Jnl. Of Advanced Networking and Applications (IJANA)Page 72
Proceedings of the UGC Sponsored National Conference on Advanced Networking and Applications,27th March 2015consists of two procedures: The packet marking procedureand graph reconstruct procedure. In the packet markingprocedure the packets randomly encode every edge of theattack graph and the graph reconstruction procedure obtainsthe constructed graph from this encoded information. Herethe constructed graph should be the same as the attackgraph. The constructed graph is the graph obtained by thePPM algorithm and attack graph is the set of paths theattack packets has been traversed.In the packet marking scheme the “identification‟field of an IP packet is modified which is 16 bits in length.A router marks last “n‟ bits of its IP address in the IPidentification field of the packet it forwards in a “n‟ bitmarking scheme. The identification filed is divided into16/𝑛 sections. For indexing section of the field mark, valueof packets TTL modulo 16/𝑛 is used. On receiving packet onone of its interface a router insert marking into identificationfield using TTL value of t he packet as an index. In case ofattack the victim can filter packets based on Pi markings.Vitim has to classify a single packet as an attack packet;victim then records the marking from same packet andfurther drops all packets carrying same marking [9].In the marking based detection and filteringscheme, A router puts its IP address into the marking spaceof each packet it receives; if there is already a number inthat space, it calculates the exclusive-or (XOR) of itsaddress with the previous value in the marking space andputs the new value back. This method ensures that themarking does not change its length when a packet travelsover the Internet, so the packet size remains constant. Tomake the marking scheme more effective, let each routerperform a Cyclic Shift Left(CSL) operation on the oldmarking Mold and compute the new marking as M CSL(Mold) MR. In this way, the order of routers influencesthe final marking on a packet received by the firewall. whena packet arrives at its destination, its marking depends onlyon the path it has traversed. If the source IP address of apacket is spoofed, this packet must have a marking that isdifferent from that of a genuine packet coming from thesame address. The spoofed packets can thus be easilyidentified and dropped by the filter, while the legitimatepackets containing the correct markings are accepted [10].4. Proposed WorkThere have been numerous techniques for filteringthe spoofed packets and tracing the attack source. But thepure host based mechanism cannot trace the attack source.To trace the attack source, the host based mechanisms haveto combine with router based mechanisms. The proposedscheme combines the two techniques, Updated Hop CountFilter and Efficient Probabilistic Packet Marking Algorithm.Updated Hop Count FilterThe Updated hop count filtering (UHCF)mechanism is used to identify the spoofed packet out ofnumerous legitimate packets. Whenever source wants toassess the authenticity of any packets then it initiates theverification modules. Initially source wants to communicatewith the destinations node then it checks its routing table. Itthe entry is found then TTL field is updated in initialmessage. If the entry is not found then it as sends theMulticast Probe RREQ message to destination. Destinationsreply with its IP Address, mapping and required details inProbe RREP message. This entry of multicast route isgetting updated in routing table. Total number of hops is thenumber of devices traversed during this datacommunications. A timer counter is attached with probemessage so as to get the validity on time which verifies theroute existence. Each device reduces the TTL value by 1when a packet is transferred from it to any other device.Now the hop count table is created at source end. Now thefiltering is applied according to which hop count iscalculated as current measured TTL value is subtractedfrom initial TTL value. Here Initial TTL value is taken fromthe OS service port number which is fixed. Now the filterselects the TTL value from the table which is just above themeasured value.Hop Distance to Source Node 255 (DefaultInitial Value)-Current TTL ValueThe hop count of received packet is calculated as t0-t. Afterthe hop count is calculated then the path is checked bycondition:Check Path Length (TTL of Stored Hop CountCalculated by Probe Message- TTL of MeasuredHop Count by Current Message) VariableThreshold Value (0 to Number of Multicast Path)&& 30;This condition is verifying the TTL value in which if thedifferentiated value is lesser than 30 than it is a legitimateroute. But in some cases route can of more hops than anaverage variable threshold is also calculated which lies inbetween each hops of multicast path. So if the multicastreply came then this condition gets activated which shouldbe above a threshold. From this multipath solution to largerhops is also feasible form up[dated HCF mechanism. Nowif the above condition is found to be correct than the packetis taken as a legitimate packet of else it is a spoofed packet.This information is then forwarded to each neighbor so thatrouting table and HCF value is updated at each nodes anddevices.Algorithm(i) Send Multicast Probe Message(ii) Reply Multicast Probe Message (Route Hop Counts 1,Route Hop Count 2, .Route Hop Counts 3)(iii) Create Hop Count Table at Hosts (IP Address, HopCounts, and Low level Interrupts timers)(iv) Probe message reply comes in a Time Limit (PathExist) Else Invalid Path(v) Apply Hop Count Filtering (Checks Spoofed Packet orNot)(vi) Hop Count Initial TTL value - Final TTL value(vii) Checks Hop Count Based on Ports Service(viii) Select the Port Number Having respective TTLMinimum Above Larger Value from the Current TTL(ix) The hop count can be calculated for the received packetas follows: (hop count) t0 t. For example, when a hostSpecial Issue Published in Int. Jnl. Of Advanced Networking and Applications (IJANA)Page 73
Proceedings of the UGC Sponsored National Conference on Advanced Networking and Applications,27th March 2015receives a packet with a TTL value of 120 (t 120), theminimum number in Table 1 that is larger than t is 128 (t0 128). Therefore, the hop count is 8 (128 120 8).(x) Hop Distance to Source Node 255 (Default InitialValue )-Current TTL Value(xi) Check Path Length (TTL of Stored Hop CountCalculated by Probe Message- TTL of Measured Hop Countby Current Message) Variable Threshold Value( 0 toNumber ofMulticast Path) && 30; the packet is legitimate;(xii) Else(xiii) Packet is spoofed;(xiv) Inform Other By Update Alarm Message (AttackConfirm)(xv) If the difference 30 Packet is legitimate or elseSpoofed(xvi) Inform Other By Update Alarm Message (AttackConfirm){If ( w.distance 0 ) thenwrite router address into w.end and 1 into flag}/* flag 1 implies that the packet has encoded an edge and noother successive routers shouldstart encoding */If (flag 1) thenIncrement w.distance by 1/* w.distance represents the distance of the encoded edgefrom the victim V */}}A victim V, upon receiving packets, first needs filtering ofunmarked packets (since they don’t carry any information inthe attack graph construction). The victim needs to executethe graph construction algorithm for all the collectedmarked packets and re-construct the attack graph.The detection rate of UHCF consistently swingsaround the optimum value of 99% which is a good sign ofpacket filtering technique. So the proposed scheme haschosen this technique to filter the spoofed packet.Attack Graph Construction Procedure at victim VEfficient Probabilistic Packet Marking AlgorithmThe efficient probabilistic packet marking (PPM)algorithm is used to discover an attack graph during adistributed denial-of-service attack. The EPPM algorithmconsists of two procedures: The packet marking procedureand graph reconstruct procedure. In the packet markingprocedure the packets randomly encode every edge of theattack graph and the graph reconstruction procedure obtainsthe constructed graph from this encoded information. Herethe constructed graph should be the same as the attackgraph. The constructed graph is the graph obtained by theEPPM algorithm and attack graph is the set of paths theattack packets has been traversed.The router determines how the packet can beprocessed depending on the random number generated. If xis smaller than the predefined marking probability pm, therouter chooses to start encoding an edge. The router sets thestart field of the incoming packet to the routers address andresets the distance field to zero. If x is greater than pm, therouter chooses to end encoding an edge by setting therouter’s address in the end field. We use an extra fieldnamed as flag which takes either 0 or 1. The flag value atfirst is made 0 and if the end field is set then the flag ismade 1. Now, the start field is encoded only when the flagis 0. If the flag is 1 it implies that the start and end fieldstogether encoded an edge of the attack graph.Marking procedure at router Rfor (each packet w received by the router){generate a random number x between [0.1);if (x pm and flag 0 ) then/* router starts marking. flag 0 implies that the packet is notencoded previously */write router’s address into w.start and 0 into w.distanceelselet G be a tree with root being victim V ;let edges in G be tuples(start,end,distance);for (each received marked packet w){if (w.distance 0) theninsert edge (w.start,V ,0) into G ;elseinsert edge (w.start, w.end, w.distance) into G ;}remove any edge (x,y,d) with d distance from x to V in G;extract path (Ri Rj) by enumerating acyclic paths in G ;A good attack traceback scheme is providingaccurate information about routers near the attack sourcerather than those near the victim. Avoiding the use of largeamount of attack packets to construct the attack path orattack tree and low processing and storage overhead atintermediate routers. For these reason, the proposed methodhas chosen the EPPM algorithm to trace the attack sourceand intimate to the neighbor routers to prevent furtherattacks.So, the proposed method combines the two abovetechniques for effectively detect, filter the spoofed pocketand also trace the attack source.5. ConclusionThe number of Internet users is increasing day byday and in the same time the threats in the Internet is alsoincreasing. So security is very important to protect the dataand systems from attackers. DDoS attack is one of thedangerous attacks. In recent years various techniques havebeen proposed for preventing data from DDoS. The Packetfiltering mechanisms are only detect and filter the attackedpacket, not trace the attacker. The Packet tracingmechanisms are only detect, block and trace the attackedpath, not filter. In the proposed method, the victim caneffectively detect, filter and also tracing the attacker. Infuture, we implement this combined approach in MANET.Special Issue Published in Int. Jnl. Of Advanced Networking and Applications (IJANA)Page 74
Proceedings of the UGC Sponsored National Conference on Advanced Networking and Applications,27th March 2015REFERENCES[1] S. Savage, D. Wetherall, A. Karlin, andT.Anderson, Practical network support for IPtraceback, in Proceeding of ACM SIGCOMM'00,Vol.30, No.4, 2000, pp. 295-306.[2] Yogesh Singh, Hariom Awasthi, Controlling IPSpoofing Through Packet Filtering UsingSimulations In Blowfish Algorithm IJPAERCSEVol. 01, Issue 01, 04, 2014.[3] Mrs. Mridu Sahu Rainey C. Lal ,Controlling IpSpoofing Through Packet Filtering, InternationalJournal of Computer Techology & Applications,Vol 3 (1) 2012.[4] www.wikipedia.com.[5] A.Bermlerand H.Levy, Spoofing PreventionMethod Proc.IEEE INFOCOM’05, 2005.[6] J. Li, J. Mirkovic, M. Wang, P. Reiher, and L.Zhang,Save:SourceAddressValidityEnforcement Protocol, Proc. IEEE INFOCOM,June 2002.[7] Cheng Jin, Haining Wang and Kang G.Shin, HopCount Filtering: An Effective Defense ta/cse/2003/CSETR-473-3.pdf[8] H.Rurch and B.Cheswick, Tracing anonymouspackets to their approximate source, in UsenixLISA, 2000.[9] Abraham Yaar, Adrian Perrig, Dawn Song, Pi: APath Identification Mechanism to Defend againstDDoS Attacks, Proceedings of the 2003 IEEESymposium on Security and Privacy (SP.03).[10] Y.Chen, “A Novel Marking-based Detection andFiltering Scheme Against Distributed Denial ofService Attack”, Masters Paper, University ofOttawa, [1] 2006.[11] Y. Bhavani, P.Niranjan Reddy, An Efficient IpTraceback Through Packet Marking Algorithm,IJNSA, Vol.2, No.3, July 2010[12] Mr.Govind M Poddar, Mr.Nitesh Rastogi, UHCF:Updated Hop Count Filter Using TTL Probing andVarying Threshold for Spoofed Packet Separation,IJERMT, Vol-3, Issue-4, April 2014.[13] Mr.Govind M Poddar, Mr.Nitesh Rastogi,Performance Evaluation of UHCF Using TTLProbing for Packet Spoofing Detection in MANET,IJAREEIE, Vol-3, Issue-8 August- 2014.Special Issue Published in Int. Jnl. Of Advanced Networking and Applications (IJANA)Page 75
redirect the blame for attacks. These spoofing packets are often part of some malicious activity, such as a DDoS attack. To thwart DDoS attacks, researchers have taken two distinct approaches: packet filtering and packet tracing. Packet filtering mechanism defines to detect and filter the attacked packet and Packet tracing mechanism defines to
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