- A
Place the application on an isolated network segment and restrict access with IP whitelisting.
Why wrong: Isolation reduces exposure but does not fix the weak NTLM authentication; credentials could still be intercepted or relayed.
- B
Deploy an authentication federation service that translates modern Kerberos/SAML to NTLM for the legacy application.
A federation service (e.g., ADFS with NTLM fallback) allows the application to use modern authentication while the broker handles the legacy protocol, reducing risk.
- C
Apply vendor patches to upgrade NTLM to NTLMv2 and enable extended protection for authentication.
Why wrong: NTLMv2 is still vulnerable to relay attacks; extended protection helps but is not a complete solution and may not be available.
- D
Disable NTLM and force the application to use Kerberos directly.
Why wrong: Legacy applications often cannot be reconfigured to use Kerberos; forcing it would break functionality.
Quick Answer
The correct approach is to deploy an authentication federation service that translates modern Kerberos or SAML to NTLM for the legacy application. This works by placing a federation proxy—such as ADFS or a SAML gateway—between the client and the legacy app, so the client authenticates with modern protocols while the proxy handles the NTLM handshake on the backend. This isolates the weak NTLM traffic to a controlled, internal segment without modifying the legacy application. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of protocol translation as a risk mitigation strategy rather than outright removal or isolation. A common trap is choosing network isolation (Option A), which does not address NTLM’s inherent vulnerabilities like pass-the-hash, or disabling NTLM entirely (Option B), which breaks the app. Remember the mnemonic “Proxy, not pry”—use a federation proxy to bridge the gap, not pry the legacy system apart.
CAS-004 Security Engineering Practice Question
This CAS-004 practice question tests your understanding of security engineering. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company's security team is reviewing the integration of a legacy application that only supports NTLM authentication. The infrastructure must be updated to meet modern security standards. Which of the following is the BEST approach to mitigate the risk of using NTLM?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Deploy an authentication federation service that translates modern Kerberos/SAML to NTLM for the legacy application.
Option D is correct because extending the application's authentication to support Kerberos or modern SSO via a federation service like ADFS or SAML proxy allows the legacy app to use modern authentication without modifying the app. Option A is wrong because network isolation does not address the weakness of NTLM in the authentication protocol. Option B is wrong because disabling NTLM would break the application. Option C is wrong because applying patches may not be possible if the application is no longer supported, and NTLMv2 is still vulnerable.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Place the application on an isolated network segment and restrict access with IP whitelisting.
Why it's wrong here
Isolation reduces exposure but does not fix the weak NTLM authentication; credentials could still be intercepted or relayed.
- ✓
Deploy an authentication federation service that translates modern Kerberos/SAML to NTLM for the legacy application.
Why this is correct
A federation service (e.g., ADFS with NTLM fallback) allows the application to use modern authentication while the broker handles the legacy protocol, reducing risk.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Apply vendor patches to upgrade NTLM to NTLMv2 and enable extended protection for authentication.
Why it's wrong here
NTLMv2 is still vulnerable to relay attacks; extended protection helps but is not a complete solution and may not be available.
- ✗
Disable NTLM and force the application to use Kerberos directly.
Why it's wrong here
Legacy applications often cannot be reconfigured to use Kerberos; forcing it would break functionality.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this CAS-004 question test?
Security Engineering — This question tests Security Engineering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Deploy an authentication federation service that translates modern Kerberos/SAML to NTLM for the legacy application. — Option D is correct because extending the application's authentication to support Kerberos or modern SSO via a federation service like ADFS or SAML proxy allows the legacy app to use modern authentication without modifying the app. Option A is wrong because network isolation does not address the weakness of NTLM in the authentication protocol. Option B is wrong because disabling NTLM would break the application. Option C is wrong because applying patches may not be possible if the application is no longer supported, and NTLMv2 is still vulnerable.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
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