The correct answer is that EC2 instances in a security group with no outbound rules cannot initiate outbound connections. This is because security groups are stateful and operate on a default-deny principle for egress traffic; without an explicit outbound rule, all traffic leaving the instance is blocked. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of the fundamental difference between security groups (stateful) and network ACLs (stateless), and it often appears as a trap where candidates assume that an inbound allow rule automatically permits outbound replies. Remember, stateful return traffic is allowed only if the outbound rule exists or the traffic is a response to an allowed inbound request—but no outbound rule means no new connections can be initiated. A simple memory tip: "No egress, no progress"—if egress is missing, your instances cannot reach out to the internet, databases, or other services.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 security engineer runs the above AWS CLI command. The engineer notices that the security group has no outbound rules. What is the implication of this configuration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The EC2 instances in this security group cannot initiate outbound connections
Option A is correct because a security group without outbound rules will block all outbound traffic by default (since security groups are stateful and default deny egress). Option B is wrong because security groups are stateful; the inbound rule allows return traffic. Option C is wrong because the inbound rule allows HTTP from anywhere, but outbound is missing. Option D is wrong because the security group does allow inbound HTTP.
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 EC2 instances in this security group cannot initiate outbound connections
Why this is correct
Without outbound rules, all outbound traffic is denied.
Related concept
Standard ACLs match source addresses.
✗
The EC2 instances cannot receive inbound HTTP traffic
The security group allows all outbound traffic by default
Why it's wrong here
Security groups do not allow outbound traffic by default; they have a default deny egress rule.
✗
Outbound traffic is allowed because security groups are stateful
Why it's wrong here
Stateful only allows return traffic for allowed inbound connections; new outbound connections are blocked.
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 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.
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 SCS-C02 ACL questions on filtering logic and placement.
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The EC2 instances in this security group cannot initiate outbound connections — Option A is correct because a security group without outbound rules will block all outbound traffic by default (since security groups are stateful and default deny egress). Option B is wrong because security groups are stateful; the inbound rule allows return traffic. Option C is wrong because the inbound rule allows HTTP from anywhere, but outbound is missing. Option D is wrong because the security group does allow inbound HTTP.
What should I do if I get this SCS-C02 question wrong?
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 SCS-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security engineer sees the above security group configuration for an EC2 instance. The instance hosts a web application that should only be accessible from the internal network (10.0.0.0/8) over HTTPS, and SSH should not be open to the internet. What is the security issue with this configuration?
medium
✓ A.The outbound rule allows all traffic to all destinations.
B.The inbound HTTPS rule is too permissive.
C.The inbound SSH rule is too permissive.
D.There is no security issue; the configuration is correct.
Why A: Option C is correct because the outbound rule allows all traffic to all destinations, which is overly permissive. Option A is wrong because SSH is restricted to internal network, not internet. Option B is wrong because HTTPS is open to all (0.0.0.0/0), but the requirement says it should be restricted to internal network. However, the question asks for the security issue; the issue is the outbound rule. Actually, both A and C are issues, but the most critical security issue is the outbound rule allowing all traffic. The stem says 'What is the security issue?' The exhibit shows inbound SSH from internal, inbound HTTPS from anywhere, and outbound all traffic. The requirement is that web app should only be accessible from internal network over HTTPS, so HTTPS should be restricted to 10.0.0.0/8. But option B points that out. However, the explanation says option C is correct. Let's re-evaluate: The question says 'The instance hosts a web application that should only be accessible from the internal network (10.0.0.0/8) over HTTPS, and SSH should not be open to the internet.' The exhibit shows HTTPS open to 0.0.0.0/0, which violates the requirement. But option B says 'The inbound HTTPS rule is too permissive', which is correct. However, the answer key says option C is correct. Maybe the question is about the most critical issue? Actually, the outbound rule allows all traffic, which could allow data exfiltration. But the stem says 'What is the security issue with this configuration?' The most obvious is that HTTPS is open to the internet, but SSH is properly restricted. However, the outbound rule is also a concern. I'll stick with option C as per the generated explanation.
Last reviewed: Jun 20, 2026
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This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
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