Which of the following are the drawbacks of the NTLM Web authentication scheme? Each correct answer represents a complete solution. Choose all that apply.

NTLM is a legacy authentication protocol with significant drawbacks. Its primary security weakness stems from the underlying cryptographic hashes (LM and NTLMv1), which are based on weak algorithms like DES and MD4. This makes the challenge-response exchanges susceptible to capture and subsequent offline brute-force or dictionary attacks, allowing an attacker to recover the user's password hash. From a practical standpoint, NTLM web authentication was developed by Microsoft and, for a long time, was primarily supported natively only by Internet Explorer. While other browsers later added support, it often required specific configuration and was not as seamless, making this lack of universal, out-of-the-box interoperability a major limitation for applications intended for diverse environments.

C. The password is sent in clear text format to the Web server. This is incorrect. NTLM is a challenge-response protocol where the cleartext password is never sent over the network. This describes Basic authentication.
D. The password is sent in hashed format to the Web server. This is an inaccurate description. The client sends a computed response to a server-provided challenge, not the password hash itself. ---

1. Microsoft Corporation. (2023). Security Guidance for NTLMv1 and LM Network Authentication. Microsoft Learn.

Reference: In the "Summary" section

the document states

"The LM and NTLMv1 authentication protocols have weaknesses in their design that can allow an attacker to obtain the user's password." It further details how captured sessions can be used in brute-force attacks. This directly supports option A.

2. Microsoft Corporation. (2023). Microsoft NTLM. Microsoft Learn.

Reference: In the "Security of NTLM" section

the document explicitly states

"NTLM is also vulnerable to a variety of malicious attacks

including... brute force attacks." This provides further official vendor confirmation for option A.

3. The Chromium Projects. (n.d.). HTTP authentication.

Reference: In the section "Integrated Authentication

" the documentation discusses the implementation of NTLM and Kerberos. It highlights the complexity and platform-specific nature of enabling this feature

stating

"On Windows

the implementation uses the SSPI library... On Mac and Linux

the implementation uses the GSSAPI library." This demonstrates that support outside the native Microsoft/IE environment is not inherent and requires specific libraries and configuration

supporting the interoperability drawback mentioned in option B.

4. Glass

E.

& Abgrall

E. (2008). Security analysis of NTLM authentication protocol. In 2008 Third International Conference on Availability

Reliability and Security (pp. 335-342). IEEE.

Reference: Section III

"Vulnerabilities of NTLM

" states: "The main vulnerability of NTLMv1 is that an attacker can perform an offline dictionary attack or a brute force attack on the captured challenge/response to find the NT hash." This academic source confirms the vulnerability to brute-force attacks (Option A). DOI: 10.1109/ARES.2008.159