# A Distributed RF Threat Sensing Architecture
## 2 Related Work
### Jamming Attacks  
Jamming as a subset of Denial of Service (DoS) is one of the most effective means to completely interrupt communication, or at least degrade the performance of wireless networks, and for this reason it is considered as a top ranked critical threat in wireless communication [11]. Therefore, it is a prime priority to identify the jamming attacks, localize the source of threat, and implement mitigation measures to prevent any harm to the system, or at least minimize the impact and the downtime of the network. The most common types of generic jamming attacks are described below and are summarized in Table 1:  
* Constant Jamming: the attacker continuously transmits a high-power signal to disrupt the communication channel. In constant jamming attacks, the jammer may either target the whole channel bandwidth or a specific fraction of it, destroying the packet reception of legitimate users and preventing them from accessing the channel [9]. As a reference, based on work presented in [12] on WiFi communications, when the network is attacked by a constant broadband jammer, a 100% packet error rate occurs when the received desired signal power is 4 dB less than the jamming signal. Respectively, when the jamming occurs with only a bandwidth of one sub-carrier spacing, WiFi communications fail when \(SJR>19\) dB [13]. This type of jamming is more easy to detect due to the constant interference it creates. * Deceptive Jamming: the malicious device sends regular, meaningful signals that mimic legitimate communications, causing the receiving devices to think they are receiving valid data. The main purpose of this type of attack is to waste the resources of the wireless network to prevent the legitimate devices from accessing the channel [14]. This can be harder to detect than constant jamming. * Random Jamming: the jammer alternates between jamming and non-jamming periods, making it more difficult to detect the source of the interference [15]. This type is not as efficient as constant jamming, but may endure for long periods as it conserves the attacker's energy while still disrupting communications. * Reactive Jamming: the attacker only transmits signals when legitimate communication is detected [16]. Due to this concept, reactive jammers are considered an energy-efficient attack strategy; however, they require tide timing constraints in order to rapidly switch from sensing mode to jamming. In practice, this can be achieved by implementing a built-in part of signal sensing or utilizing a third-party packet detection module. More detailed research work in this direction is presented in [17; 18]. This method makes it harder to identify the jammer since the interference only occurs intermittently. * Selective Jamming: the attacker targets specific types of communications, such as control channels or particular frequencies, by exploiting their knowledge of the targeted wireless network and the implementation details of network protocols at various layers of the protocol stack [19]. This can cause significant disruption with minimal effort, as critical components of the network are affected. * Pulse Jamming: the attacker sends short bursts of high-power signals. This type of jamming can be very effective against certain types of modulation schemes and is challenging to counteract. Several countermeasure methods have been presented in the research community. For example, [20] investigates the challenge of anti-jamming communication in a random pulse jamming environment. The authors employ the Markov decision process (MDP) to model and analyze the countermeasure in the time domain, proposing an anti-pulse jamming algorithm based on reinforcement learning. In this way, they enable the transmitter to switch between two states--\"active\" and \"silent\"--to avoid random pulse jamming. Researchers in [21] propose the Swarm intelligence algorithm to adapt change in network topology and traffic, especially for IEEE 802.15.4 wireless networks.