A public blockchain is a distributed ledger that many independent nodes replicate and validate through network consensus. Because no single server owns the record, data written to the chain is widely available and difficult to alter once finalized. Common examples include chains used for payments, smart contracts, and other decentralized applications.
In cyber security, this matters because the same resilience that protects legitimate services can also help attackers. Malware can place command data, tasking, or configuration in on-chain records instead of on one removable host. That makes simple takedowns less effective: deleting a domain or seizing a server may not remove instructions already published to the ledger. Defenders look for unusual RPC traffic, suspicious contract reads, and endpoint behavior that has no normal reason to interact with blockchain infrastructure.