Offline guessing is the process of testing many password candidates against captured credential material, such as a password hash or challenge-response value, without sending repeated login attempts to the target. Because the attacker works on copied data rather than a live authentication service, the target usually cannot detect or rate-limit each guess.
This matters because stolen or leaked hashes can still be useful even when plaintext passwords are not exposed. In attacks against server management interfaces such as BMC or IPMI, a hash-disclosure flaw may give an attacker material to crack passwords offline. Defenders reduce the risk with strong unique passwords, modern hashing or challenge protocols, restricted access to management networks, and rapid patching of vulnerable firmware. If the captured material is weak or reusable, offline guessing can turn a disclosure bug into a real compromise.