312-50V9 · Question #582
Windows LAN Manager (LM) hashes are known to be weak. Which of the following are known weaknesses of LM? (Choose three)
The correct answer is A. Converts passwords to uppercase. B. Hashes are sent in clear text over the network. D. Effective length is 7 characters. LAN Manager hashes are weak because they convert passwords to uppercase, transmit hash responses over the network where they can be captured, and split passwords into two independent 7-character halves before hashing.
Question
Windows LAN Manager (LM) hashes are known to be weak. Which of the following are known weaknesses of LM? (Choose three)
Options
- AConverts passwords to uppercase.
- BHashes are sent in clear text over the network.
- CMakes use of only 32 bit encryption.
- DEffective length is 7 characters.
How the community answered
(16 responses)- A88% (14)
- C13% (2)
Why each option
LAN Manager hashes are weak because they convert passwords to uppercase, transmit hash responses over the network where they can be captured, and split passwords into two independent 7-character halves before hashing.
LM hashes convert the entire password to uppercase before processing, eliminating case sensitivity and drastically shrinking the effective keyspace an attacker must search.
During NTLM challenge-response authentication, the LM hash-derived response is sent across the network and can be captured by an attacker for offline cracking without ever needing to touch the server again.
LM uses 56-bit DES encryption, not 32-bit; the critical weaknesses are the uppercase normalization, network exposure of the hash response, and the 7-character split - not the DES key length label.
LM pads the password to 14 characters and then splits it into two separate 7-character halves, each hashed independently with DES, meaning an attacker only ever needs to crack a maximum of 7 characters at a time rather than the full password.
Concept tested: Windows LAN Manager hash structural weaknesses
Source: https://learn.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/network-security-do-not-store-lan-manager-hash-value-on-next-password-change
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