Encryption is challenging to security monitoring because it can be used by threat actors as a method of evasion and obfuscation. Encryption can prevent security devices from inspecting the content or payload of the network traffic, making it difficult to detect malicious activity or signatures. Encryption can also hide the source and destination of the traffic, making it hard to trace the origin or destination of the attack. Reference: https://learningnetworkstore.cisco.com/on-demand-e-learning/understanding-cisco-cybersecurity-operations-fundamentals-cbrops-v1-0/CSCU-LP-CBROPS-V1-028093.html (Module 4, Lesson 4.1.1)