Page 2 Lecture Notes in Computer Science 2865 Edited by G. Goos ...

142 J. Zhen and S. SrinivasTraffic Analysis: Resource limitations make it difficult to incorporate strongencryption mechanisms into wireless data transmissions. Furthermore, mutablefields in the routing packets such as hop count are not authenticated. This mayresult in exposure of information by traffic analysis.Routing Loop: By impersonating other hosts’ Medium Access Control (MAC)addresses and falsifying favored packets (such as those with higher sequence numbersor shorter hop counts), attackers can make routes to form a loop. This typeof attack has become less likely as a result of node authentication mechanismsproposed recently [4].Black/Gray Hole: By falsely claiming they have optimal routes to multipledestinations, attackers can manage to make relative amount of routes pass bythem so as to manipulate packets later on. This attack has been solved by Denget. al. [18].Detour: Malicious nodes operate on packets illegally, such as by changing hopcounts and sequence numbers arbitrarily, to poison routing tables and make itimpossible for optimal routes to be chosen. Some solutions have been proposedbut they only solve part of the problem [4].Fake RERR(Route Error): A malicious node claims that an actually wellconnectednode is now unreachable by forging RERR packets. This RERR mayhave a high sequence number (fresher than any other) such that nodes will notaccept any opposite information (such as RREQ to/from the isolated node).Injection of Extra Control Packets: Injected control packets will result inunnecessary network operations. For example, injected RREQ will cause thenetwork to be flooded without the need for data transmission, thus resulting ina denial of service attack. This can be solved by authenticating the source of theRREQ packets [15].General Replay Attacks: Intruder nodes can launch attacks on the ad hocnetwork by replaying routing packets. While general authentication mechanismscannot prevent replay attacks, the sequence number and the RREQ ID fieldsare designed to reduce their possibility. However, there are two types of replayattacks that are particularly challenging to defend against. We describe these inthe next section.2.3 Two Special Replay AttacksRREQ Flooding Attack. We identify a potential replay attack on the AODVprotocol. The RREQ packets are broadcast in an incrementing ring to reduce