Hybrid encryption is a cryptographic design that combines symmetric and asymmetric methods. In ransomware, the malware usually creates a fast symmetric key to encrypt files and then protects that key with an attacker-controlled asymmetric public key. The result is efficient file locking at scale, while the private key needed for recovery stays only with the attacker.
This matters because it makes ransomware difficult to undo without backups or a decryption tool. Symmetric encryption is fast enough to process many files and network shares, while asymmetric encryption prevents defenders from simply extracting the key from the malware. In real intrusions, hybrid encryption often appears after access has already been gained through exposed remote services, stolen credentials, or lateral movement. Defenders look for mass file changes, ransom-note drops, and attempts to delete backups, then isolate systems and restore from clean offline copies.