In the following, we describe the various attacks in more detail.
2.1 Physical Layer Attacks
Jamming
Jamming is a well-known attack on wireless communication, and it interferes
with the radio frequencies that are used by nodes in a network. A small number
of randomly distributed jamming nodes can disrupt the entire network, and
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Xiaojiang Du and Yang Xiao
Fig. 1. Typical Attacks on Sensor Networks.
cause all the nodes in the network to be out of service. There are many lowcost
devices available in the market which can be used for jamming purpose.
For sensor networks using single radio frequency, the jamming attack is simple
and e?®ective.
The standard defense against jamming involves various forms of spreadspectrum
communication. To attack frequency hoppers, the adversary must
be able either to follow the precise hopping sequence or to jam a wide section
of the band. Mobile-phone networks commonly use code spreading as
a defense against jamming. Since spread-spectrum communication requires
greater design complexity and more power, low-cost, low-power sensor nodes
may not be able to use this technique. Sensor nodes can defend intermittent
jamming attacks by switching to a lower duty cycle and conserving as much
power as possible. Periodically, the nodes can wake up and check whether the
jamming has ended. By spending energy frugally, the nodes may be able to
outlive an adversary, who must continue to jam at greater expense [13].
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