In this section, we give an overview of some attacks on wireless sensor networks, and vehicular communications.
Attacks on Wireless Sensor Networks Sensor networks are particularly vulnerable to
several types of attacks. Attacks can be performed in a variety of ways ranging from denial of service to delayed authentication compromise, physical attacks, sybil attacks, wormhole attacks, and so on. In the following, we present some major attacks on WSNs, that could also be applied to vehicular communications.
• Denial of Service Attacks.
A standard attack is simply to jam a node or a set of nodes. Jamming consists in this case to the transmission of a radio signal that interferes with the radio frequencies being used by the network [56]. There are two forms of jamming a network: Constant jamming and Intermittent jamming. The former (Constant jamming) involves the complete jamming of the entire network. No messages are able to be sent or received. In Intermittent jamming, nodes are able to exchange periodically but not consistently.
This can have an impact on the sensor network when exchanged messages between nodes are time sensitive [56].
Denial of service attacks assume a particular importance in wireless sensor networks, where it is not possible to afford the computational overhead necessary in implement- ing many of the typical defensive strategies of traditional computing. Attacks can be made on the link layer itself. For instance, an attacker may simply intentionally vio- late the communication protocol, e.g., ZigBee [57], or IEEE 801.11b (Wi-Fi) protocol, and then transmit messages continually in an attempt to generate collisions. Thus, the collisions would require the retransmission of any packet affected by the collision. Using this technique, an attacker can easily deplete a node’s power supply by doing many retransmissions.
The routing layer is also susceptible to DoS attacks. A node can take advantage of a multi hop network by simply refusing to route messages constantly or intermittently. In the transport layer, the malicious node can opt to flooding. Flooding can be as simple as sending many connection requests to a susceptible node. In this case, resources must be allocated to handle the connection request. As a result, the node’s resources will be exhausted. Finally, a denial of service attack can be performed against the specific application level protocol.
We address the DoS attack in Chapter 2, and we demonstrate that authentication delay in µTESLA based schemes could lead to a memory DoS attack. In Chapter 5, we address also this kind of attack when analyzing the security threats to a state of the art multi-hop broadcast algorithm for vehicular communications.
• Delayed Authentication Compromise Attack. In order to present the delayed authentication compromise attack, let us consider the scenario when the receiver needs to log the received messages, in such a way that an attacker cannot successively modify the messages. Key disclosure based schemes (µTESLA based schemes) are not candidates to be used in such scenario. Indeed, as soon as the key is disclosed, the attacker may use that key to modify the logged messages. In [18], this attack process refers to Delayed Authentication Compromise (DAC) attack. The adversary may use an already disclosed key to sign for instance the command “open the valve”, and save it in the memory of a compromised actuator. Once noticed that the valve has been opened, it will be difficult to prove with certainty who has been compromised. If the base station is trusted, we can state that the node is cheating; however if the base station itself can be compromised, then it is not possible to determine who is cheating, the node or the base station. We present the DAC attack in Chapter 3, and we demonstrate that several issues are still not properly addressed.
Attacks on Vehicular Communications The major attacks on vehicular communi-
cations could be classified into Bogus Information, Cheating Positioning information, ID disclosure of other vehicles, Denial of Service, and Masquerade [39]. In the following we present a brief overview of these attacks.
• Bogus information. One or several legitimate members of the network send out false information to misguide other vehicles about traffic conditions. In order to cope with such misbehavior, the received data from a given source should be verified by correlating and comparing them with those received from other sources.
• Cheating on positioning information. Injection of a false position by a malicious vehicle pretending to be at a claimed position.
• ID disclosure of other vehicles. This is to track their location. A global entity can monitor trajectories of targeted vehicles and use this data for many purposes, we could take the example of some car rental companies that track their own cars. • Denial of Service. Wood and Stankovic define the denial of service attack as “any
event that diminishes or eliminates a network’s capacity to perform its expected func- tion” [56]. The attacker may want to bring down the Inter-Vehicular Communication (IVC) or even cause an accident. Example of attacks include channel jamming and aggressive injection of dummy messages.
• Masquerade. The attacker claims to be another vehicle by using false identities. In Chapter 5, we study a state of the art algorithm for vehicular safety, and we demonstrate its vulnerability to different attacks.