## 3 Countermeasures
### Intrusion Detection-Based Countermeasures
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & **Threat Area** & **Countermeasure** & **Attributes** & **Limitations** \\ \hline
[32] & Integrity & Context-aware security & \(\bullet\) & Physical layer security & \(\bullet\) & Backward Compatibility \\  & & \(\bullet\) & Wireless edge awareness & \(\bullet\) & Physical Layer Processing \\  & & \(\bullet\) & Adaptive protocols & \(\bullet\) & Degradation in \\  & & & & & interference/jamming \\ \hline
[46] & Authentication & QR code & \(\bullet\) & Secret sharing scheme & \(\bullet\) & QR security issues, such as Q \\  & & & \(\bullet\) & Secret image shadows based on & & phishing, replacement of \\  & & & & polynomial & QR code \\  & & & \(\bullet\) & RS encoding for secret recovery & & \\ \hline
[80] & Authentication & Quantum key distribution & \(\bullet\) & Simulation scheme for the & \(\bullet\) & Simulation solution \\  & & & \(\bullet\) & quantum key distribution & \(\bullet\) & Specific to MitM only \\  & & & \(\bullet\) & Final length key for symmetrical & \(\bullet\) & Integration with higher layer in \\  & & & encryption & & network \\ \hline
[81] & Authentication & 3D location & \(\bullet\) & Spectrum matching game & \(\bullet\) & Subject to GPS spoofing \\  & & & \(\bullet\) & UAV based communication & \(\bullet\) & Regulatory Issues \\  & & & \(\bullet\) & strengthening & & \\  & & & \(\bullet\) & Mixed integer nonlinear & & \\  & & & programming & & \\ \hline
[86] & Confidentiality & Conditional Attributes & \(\bullet\) & Bloom filter-based private set & \(\bullet\) & High communication overhead \\  & & & \(\bullet\) & intersection & \(\bullet\) & Scalability issues \\  & & & \(\bullet\) & Conditional privacy preservation & \(\bullet\) & High computational cost \\ \hline
[87] & Availability & Physical layer attributes & \(\bullet\) & Reconfigurable surfaces-based & \(\bullet\) & Specific to DoS attack only \\  & & & multi-antenna & \(\bullet\) & Complexity \\  & & & \(\bullet\) & Beamforming & \(\bullet\) & Scalability \\ \hline
[84] & Confidentiality & Antenna selection & \(\bullet\) & Joint utilization of optical and & \(\bullet\) & Limited to eavesdropping attack \\  & & & RF links & & MIMO technology \\  & & & \(\bullet\) & Probabilistic secrecy analysis & \(\bullet\) & Compatibility with \\  & & & \(\bullet\) & Monte Carlo simulations & & heterogenous networks \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Entity Attribute countermeasures for 6G communication. intelligent detection of attacks, such as jamming, malware, DoS or DDoS [95]. In [48], the authors presented a moving target defense mechanism for proactive defense against multiple attacks including MitM. However, the study has considered only the wireless domain and compatibility issues with the upper layer in a network. Similarly, in [51], the authors suggested a novel approach for IDS to counter several attacks including MitM, showing 99.99% performance of the proposed ML algorithm against various threats. However, the proposed study needs evaluation for suitability in heterogenous networks. Cognitive radio-enabled 6G networks bring various opportunities and challenges through automated security techniques to counter malicious intrusion in communication paths [96; 97]. 6G physical layer manipulation is an extreme point of interest for both attackers and security solution designers. At one end, where vast bandwidth and heterogenous connectivity create favorable grounds for the attacker, 6G spectrum monitoring provides intelligent neural network-based prediction of Secrecy Outage Probability (SOP). SOP is an important criterion for evaluating network secrecy performance [98]. An SDN-enabled blockchain-based resource allocation scheme can provide a secure ecosystem in 6G networks through smart contracts [99]. Secure resource allocation builds an intrusion-proof foundation and trusted network architecture [100]. Similarly, blockchain-based secure data aggregation enables distributed data-dependent industrial applications [101].