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mediocre hardware, which is usually not tamper-resistant. Hence, nodes can easily be
compromised by attackers, leading to a completely new set of attacks. In this chapter,
we review the different kinds of attacks that can be carried out on WSN and then
briefly look into state-of-the-art security in WSN.
2.2 Attacks on WSN
Wireless sensor networks are a subclass of wireless networks in general, so most kinds
of attacks that can be directed at wireless networks can be directed at WSN. However,
due to the additional challenges as discussed in Chapter 1, WSN breed a whole new
set of attacks that can be classified into “mote-class attacks” and “laptop-class attacks”
(Karlof and Wagner 2003). In a mote-class attack, the attacker takes control of a few
compromised nodes and has capacity no greater than that of these ordinary sensor
nodes. Hence, he has to launch attacks without depleting his resources (storage, com-
putation, and bandwidth). Moreover, the attacker is restricted in his coverage due to
limited transmission power. In contrast, the laptop-class attacker is resource-abundant
(high transmitting power, longer battery life, high-speed processors, and highly recep-
tive omnidirectional antennae). Hence, he has greater coverage and diversity in terms
of the attacks that he can launch. Figure 2.1 portrays the attack taxonomy for WSN,
while Table 2.1 shows the attack classification through a layered approach.
In general, attacks can be divided into active and passive attacks.
Passive attack: In this type of attack, the attacker is able to intercept and moni-
tor data between communicating nodes, but does not tamper or modify packets
for fear of raising suspicion of malicious activity among the nodes. For example,
in traffic analysis, the attacker may not be able to decode encrypted data, but
can find useful information by analyzing headers of packets, their sizes, and the
frequency of transmission. In WSN, reconnaissance can also be performed to
understand information exchange between communicating nodes, particularly
at data aggregation points. Furthermore, routing information can be exploited
using traffic analysis.
Active attack: In this type of attack, the attacker actively participates in all forms
of communication (control and data) and may modify, delete, reorder, and replay
messages or even send spoofed illicit messages to nodes in the network. Some
other active attacks include node capturing, tampering with routing informa-
tion, and resource exhaustion attacks. Peculiar to WSN, the attacker can modify
the environment surrounding sensors, which could affect the sensed phenomena.
2.2.1 Threats to Privacy
In WSN, threats to privacy can be further classified into reconnaissance and
eavesdropping.
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