Security is a critical prerequisite for some types of applications in sensor networks, especially since they are often deployed in harsh environments, unmanned areas, or enemy positions. Due to the inherent vulnerabilities of wireless networks, ensuring security in sensor networks is a major concern. Many applications, such as military target monitoring and tracking, rely heavily on the secure operation of the network. If a sensor network is attacked or destroyed, it can lead to catastrophic consequences. Creating a relatively safe working environment for sensor networks by designing security mechanisms that provide confidentiality protection and identity authentication functions despite limited node computing speed, power supply, communication capacity, and storage space is a key issue related to whether the sensor network can be practical.

1. Physical layer attack and defense:

(1) Congestion attack: An attack node continuously sends unnecessary signals on the working frequency band of the sensor network, preventing the sensor nodes in the attack node from functioning normally. Congestion attacks are particularly effective for single-frequency wireless communication networks. To defend against single-frequency congestion attacks, broadband and frequency hopping methods can be used. For full-band continuous congestion attacks, switched communication modes and optical or infrared communication are effective alternatives.

(2) Physical tampering: The enemy can capture a node and obtain sensitive information such as an encryption key, allowing unrestricted access to upper-layer information. To mitigate unavoidable physical damage, defensive measures such as increasing physical damage awareness mechanisms, destroying sensitive data after node destruction is detected, leaving the network, modifying security procedures, encrypting and storing sensitive information, and tightly protecting communication encryption keys, authentication keys, and various secure activation keys can be taken.

2. Link layer attack and defense:

(1) Collision attack: If two devices transmit simultaneously in a wireless network environment, their output signals cannot be separated due to overlap. This results in packet collisions during transmission, causing the entire packet to be discarded. This type of collision is called a collision in the link layer protocol. Error correction coding, channel monitoring, and retransmission mechanisms can be used to defend against collision attacks.

(2) Exhaustion attack: This refers to the use of protocol vulnerabilities to exhaust node energy resources through continuous communication. One way to deal with exhaustion attacks is to limit the speed at which the network is sent so that nodes automatically discard excessive data requests. Another method is to formulate execution strategies when implementing the protocol, such as ignoring excessively frequent requests or limiting the number of packet retransmissions to avoid energy depletion caused by endless interference from malicious nodes.

(3) Unfair competition: If network packets have priority control over the communication mechanism, malicious or captured nodes may continuously send high-priority packets on the network to occupy the channel, causing other nodes to be disadvantaged in the communication process. Implementing a short packet strategy or using competitive or time-division multiplexing methods instead of a priority policy can mitigate this type of attack.

3. Network layer attacks and defenses:

Each node in a sensor network is both a terminal node and a routing node, increasing its vulnerability to attack. Security issues of the transport layer and the application layer are often specific to the system and will not be described in detail here.

4. Security threats to the sensor network routing layer:

Attackers can be divided into mote.class attacks and laptop.class attacks based on their capabilities. Dust-level attackers have similar capabilities to the sensor node, while attackers at the computer level typically have more battery power, CPU computing power, sophisticated wireless signaling devices, and antennas.

5. Solutions for various threats at the routing layer:

Most external attacks against the routing layer can be defended by link layer encryption and authentication mechanisms that use global shared keys. Encrypting data packets prevents attackers from forging or tampering with them, while adding a timestamp can prevent the replay of previous packets. Applying a common-mode key at the data link layer to encrypt the data packet provides an additional layer of security.

6. Application layer various threat solutions:

Application layer research mainly focuses on providing security support for the entire wireless sensor network, namely key management and secure multicast research. Wireless sensor networks are widely used, and it is crucial to have robust security mechanisms to ensure their safe operation.