Question 357 of 851

Secure, monitor, and optimize data storage and data processing →mediumMultiple ChoiceObjective-mapped

Why Customer-Managed Key Encryption Fails Due to Key Vault Firewall

This DP-203 practice question tests your understanding of secure, monitor, and optimize data storage and data processing. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

Your company uses Azure Data Lake Storage Gen2 for a data lake. You need to implement a security strategy that meets the following requirements: 1) All data must be encrypted at rest using customer-managed keys stored in Azure Key Vault. 2) Access to the storage account must be restricted to specific virtual networks. 3) Users must authenticate using Microsoft Entra ID and be granted read-only access to the 'landing' container. You have configured the storage account with Azure Storage Service Encryption (SSE) using customer-managed keys. You have also configured firewall rules to allow access only from the required virtual network. However, users cannot access the 'landing' container even though they have the Storage Blob Data Reader role. What is the most likely issue?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

A
The users have not been granted access to the Key Vault
Why wrong: Users don't need direct Key Vault access; storage account does.
B
The users do not have the Storage Blob Data Reader role assigned at the container scope
Why wrong: Role assignment is correct.
C
The firewall is blocking the users' IP addresses even though they are in the virtual network
Why wrong: Firewall allows the virtual network.
D
The Key Vault firewall is blocking access from the storage account
Key Vault firewall must allow Azure services or specific storage account.

Full breakdown with real-world context →

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

✓

The Key Vault firewall is blocking access from the storage account

The most likely issue is that the Key Vault firewall is blocking access from the storage account. When using Azure Storage Service Encryption (SSE) with customer-managed keys, the storage account must be able to access the Key Vault to wrap and unwrap the encryption key. Even though the users have the Storage Blob Data Reader role and the storage account firewall allows the virtual network, if the Key Vault firewall does not permit access from the storage account (e.g., via 'Allow trusted Microsoft services' or a specific network rule), the storage service cannot decrypt the data, resulting in access failures. Option D correctly identifies this. Options A and B are incorrect because the users have the correct RBAC role and the role is effective at the storage account level; the issue is not with user permissions but with the storage account's ability to reach the Key Vault. Option C is incorrect because the firewall rules are correctly configured for the virtual network.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The users have not been granted access to the Key Vault
Why it's wrong here
Users don't need direct Key Vault access; storage account does.
✗
The users do not have the Storage Blob Data Reader role assigned at the container scope
Why it's wrong here
Role assignment is correct.
✗
The firewall is blocking the users' IP addresses even though they are in the virtual network
Why it's wrong here
Firewall allows the virtual network.
✓
The Key Vault firewall is blocking access from the storage account
Why this is correct
Key Vault firewall must allow Azure services or specific storage account.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

Real-world example

How this comes up in practice

A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

Quick reference

Access Control Model Comparison

Model	Acronym	Who Controls Access?	Best For
Discretionary Access Control	DAC	Resource owner	Small teams, file shares
Mandatory Access Control	MAC	System / security labels	Classified govt / military
Role-Based Access Control	RBAC	Administrator (via roles)	Enterprise environments
Attribute-Based Access Control	ABAC	Policy engine (user + resource attributes)	Fine-grained, dynamic policies
Rule-Based Access Control	RuBAC	System rules / ACLs	Firewall rules, network ACLs

What to study next

Got this wrong? Here's your next step.

Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DP-203 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this DP-203 question test?

Secure, monitor, and optimize data storage and data processing — This question tests Secure, monitor, and optimize data storage and data processing — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: The Key Vault firewall is blocking access from the storage account — The most likely issue is that the Key Vault firewall is blocking access from the storage account. When using Azure Storage Service Encryption (SSE) with customer-managed keys, the storage account must be able to access the Key Vault to wrap and unwrap the encryption key. Even though the users have the Storage Blob Data Reader role and the storage account firewall allows the virtual network, if the Key Vault firewall does not permit access from the storage account (e.g., via 'Allow trusted Microsoft services' or a specific network rule), the storage service cannot decrypt the data, resulting in access failures. Option D correctly identifies this. Options A and B are incorrect because the users have the correct RBAC role and the role is effective at the storage account level; the issue is not with user permissions but with the storage account's ability to reach the Key Vault. Option C is incorrect because the firewall rules are correctly configured for the virtual network.

What should I do if I get this DP-203 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Standard ACLs match source addresses.

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