Wireless Sensor Network Security

While the future of WSNs is very prospective, WSNs will not be
successfully deployed if security, dependability and privacy issues are
not addressed adequately. These issues become more important
because WSNs are usually used for very critical applications.
Furthermore, WSNs are very vulnerable and thus attractive to attacks
because of their limited prices and human-unattended deployment.
Security Requirements:
 Confidentiality (encryption)
 Integrity (e.g., identity Management, digital signatures)
 Availability (protection from denial of Service).
Introduction

Data Confidentiality
Data confidentiality is the most important issue in network security.
Every network with any security focus will typically address this
problem first. In sensor networks, the confidentiality relates to the
following :
 A sensor network should not leak sensor readings to its
neighbors. Especially in a military application, the data stored in
the sensor node may be highly sensitive
 it is extremely important to build a secure channel in a wireless
sensor network.

Data Integrity
With the implementation of confidentiality, an adversary
may be unable to steal information. However, this doesn’t
mean the data is safe. The adversary can change the data,
so as to send the sensor network into disarray. For
example, a malicious node may add some fragments or
manipulate the data within a packet. This new packet can
then be sent to the original receiver. Data loss or damage
can even occur without the presence of a malicious node
due to the harsh communication environment. Thus, data
integrity ensures that any received data has not been
altered in transit.

Adjusting the traditional encryption algorithms to fit within the wireless
sensor network is not free, and will introduce some extra costs. But all
these approaches weaken the availability of a sensor and sensor
network for the following reasons:
 Additional computation consumes additional energy .
 Additional communication also consumes more energy .
 A single point failure will be introduced if using the central point
scheme .
Availability

Challenges
For WSNs to become truly ubiquitous, a number of challenges must
be overcome. Challenges and limitations of wireless sensor networks
include the following:
 Limited functional capabilities, including problems of size
 Power factors
 Node costs
 Environmental factors
 Transmission channel factors
 Topology management complexity and node distribution

 Encryption-decryption techniques meant for the
traditional wired networks are not capable in
WSN.
 Wireless sensor networks consist of tiny sensors
which really suffer from the lack of processing,
memory and battery power.
 Applying any encryption scheme requires
transmission of extra bits.
Cryptography

 Steganography
WSN is not directly related to steganography and processing
multimedia data (like audio, video) with the inadequate
resources of the sensors is difficult.

Taxonomy of Attacks
 Wireless networks are vulnerable to security attacks
due to the broadcast nature of the transmission
medium.
 Furthermore, WSNs have an additional vulnerability
because nodes are often placed in a hostile or
dangerous environment where they are not
physically protected.
 For a large-scale sensor network, it is impractical to
monitor and protect each individual sensor from
physical or logical attack. Attackers may device
different types of security threats to make the WSN
system unstable

WSN attacks categorized at different layers:
A. Physical layer: Attacks at the physical layer include jamming and tampering.
Jamming: Jamming is a type of attack which interferes with the radio frequencies that
a network’s nodes are using .An attacker sends some radio waves at the same
frequency that it is used by wireless sensor networks .A jamming source may either be
powerful enough to disrupt the entire network or less powerful and only able to disrupt
a smaller portion of the network.

Tampering: Another physical layer attack is tampering . Given
physical access to a node, an attacker can extract sensitive
information such as cryptographic keys or other data on the
node. The node may also be altered or replaced to create a
compromised node which the attacker controls.

B. Data link layer: Attacks at the link layer include collisions, resource exhaustion.
1- Collisions: A collision results when two nodes trying to send data on same frequency.
When packets collide, a change will likely occur in the data portion, causing a checksum
mismatch at the receiving end. packet will then be discarded as invalid. An adversary may
strategically cause collisions in specific packets such as ACK control messages. A possible
result of such collisions is the costly exponential back-off. The adversary may simply violate
the communication protocol and continuously transmit messages in an attempt to
generate collisions .
2- Exhaustion: Repeated collisions can also be used by an attacker to cause resource
exhaustion . For example, a naive link-layer implementation may continuously attempt to
retransmit the corrupted packets. Unless these hopeless retransmissions are discovered or
prevented, the energy reserves of the transmitting node and those surrounding it will be
quickly depleted

C. Network layer: The attacks in the network layer include the following:
1. Spoofed, Altered, or Replayed Routing Information: The most direct attack
against a routing protocol in any network is to target the routing information itself
while it is being exchanged between nodes. An attacker may spoof, alter, or replay
routing information in order to disrupt traffic in the network . These disruptions
include the creation of routing loops, attracting or repelling network traffic from
select nodes, extending and shortening source routes, generating fake error
messages, partitioning the network, and increasing end-toend latency.

2- Selective Forwarding: A significant assumption made in multihop networks is that all
nodes in the network will accurately forward received messages. An attacker may create
malicious nodes which selectively forward only certain messages and simply drop others
One form of this attack is Black hole
3- Sinkhole: In a sinkhole attack, an attacker makes a compromised node look more attractive
to surrounding nodes by forging routing information . The end result is that surrounding
nodes will choose the compromised node as the next node to route their data through. This
type of attack makes selective forwarding very simple, as all traffic from a large area in the
network will flow through the adversary’s node.

4- Sybil: The Sybil attack is a case where one node presents more than one
identity to the network . It was originally described as an attack intended to
defeat the objective of redundancy mechanisms in distributed data storage
systems in peer-to-peer networks . A Sybil attack is attack in which an attacker
destabilizes the reputation scheme of a peer-to-peer network by creating a huge
number of pseudonymous entities, using them to gain a disproportionately big
influence

5- Wormhole attack: Wormhole attack needs to insert at least two
malicious nodes in the network and these nodes are connected by
a powerful connection wormhole is low latency link between two
portions of a network over which an attacker replays network
messages . This link may be established either by a single node
forwarding messages between two adjacent but otherwise non-
neighboring nodes or by a pair of nodes in different parts of the
network communicating with each other.

Hello Flood Attacks: An attacker sends or replays a routing protocol’s HELLO packets
from one node to another with more energy. This attack uses HELLO packets as a
weapon to convince the sensors in WSN. In this type of attack an attacker with a high
radio transmission range and processing power sends HELLO packets to a number of
sensor nodes that are isolated in a large area within a WSN. The sensors are thus
influenced that the adversary is their neighbor. As a result, while sending the
information to the base station, the victim nodes try to go through the attacker as they
know that it is their neighbor and are ultimately spoofed by the attacker

D. Transport layer: Two possible attacks in this layer, flooding and desynchronization,
Flooding: Whenever a protocol is required to maintain state at either end of a connection
it becomes vulnerable to memory exhaustion through flooding . An attacker may
repeatedly make new connection requests until the resources required by each
connection are exhausted or reach a maximum limit. In either case, further legitimate
requests will be ignored

Wireless Sensor Network Security

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