What are the three tiers of security?

Could you elaborate on the concept of the three tiers of security in the realm of cryptocurrency and finance? How are these tiers structured, and what role do they play in ensuring the safety and integrity of digital assets? Are there any specific measures or protocols that are associated with each tier, and how do they contribute to a comprehensive security framework? Additionally, how do these tiers interact with each other to provide a robust security system for cryptocurrency users and investors?