The answer is to use private IP addresses for instances and remove the default egress rule. These two actions enforce least privilege by ensuring instances communicate only over internal, non-routable IPs and that outbound traffic is explicitly restricted rather than allowed to any destination, including the internet. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of VPC network security best practices and the default firewall’s overly permissive egress rule, which is a common trap—candidates often overlook that the default allow-egress rule exists and must be removed to prevent data exfiltration. A reliable memory tip is “lock the door and close the window”: private IPs lock inbound exposure, while removing the default egress closes the unrestricted outbound window.
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 is migrating workloads to Google Cloud and wants to ensure that their VPC network is secure by default. Which two best practices should they follow? (Choose two.)
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the default firewall rules that allow all egress
Option A is correct because the default VPC firewall rules include an egress rule that allows all outbound traffic (target: all instances, action: allow, protocol: all, destination: 0.0.0.0/0). Removing this default egress rule and replacing it with more restrictive outbound rules is a security best practice to prevent unauthorized data exfiltration and limit outbound connections to only necessary destinations. This aligns with the principle of least privilege for network traffic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Remove the default firewall rules that allow all egress
Why this is correct
Default egress allow can be risky; removing it enforces least privilege.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Shared VPC for all projects
Why it's wrong here
Shared VPC is an organizational choice, not a security best practice by itself.
✗
Create a firewall rule to deny all ingress except specific ports
Why it's wrong here
The implicit deny already blocks all ingress; explicit deny is not needed.
✗
Enable VPC Flow Logs
Why it's wrong here
Flow logs are for monitoring and audit, not for enforcing security by default.
✓
Use private IP addresses for instances
Why this is correct
Reduces exposure to internet attacks.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that the default VPC firewall rules are secure by default, but the trap here is that the default egress rule is permissive (allow all), not restrictive, so candidates may overlook the need to remove or override it.
Detailed technical explanation
How to think about this question
Under the hood, Google Cloud VPCs have an implicit firewall rule that denies all ingress traffic and an implicit rule that allows all egress traffic. The default egress rule (target: all instances, action: allow, protocol: all, destination: 0.0.0.0/0) is explicit and can be removed, but the implicit egress allow cannot be removed; however, you can create a higher-priority deny rule to override it. In a real-world scenario, a compromised instance could use the default permissive egress to communicate with a command-and-control server, so removing the default egress rule and adding granular allow rules for specific destinations (e.g., only to required APIs or on-premises ranges) is critical for defense in depth.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Remove the default firewall rules that allow all egress — Option A is correct because the default VPC firewall rules include an egress rule that allows all outbound traffic (target: all instances, action: allow, protocol: all, destination: 0.0.0.0/0). Removing this default egress rule and replacing it with more restrictive outbound rules is a security best practice to prevent unauthorized data exfiltration and limit outbound connections to only necessary destinations. This aligns with the principle of least privilege for network traffic.
What should I do if I get this PCSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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