SCS-C02 Infrastructure Security Practice Test 18 — 15 Questions

Question 1

Refer to the exhibit. A security engineer reviews this CloudFormation template. Which statement about the bucket's public accessibility is correct?

Accepted Answer

The bucket is private because PublicAccessBlockConfiguration blocks all public access.. The PublicAccessBlockConfiguration blocks all public access settings, including bucket policies that grant public access. Even though the bucket policy allows GetObject from a specific IP range, the RestrictPublicBuckets setting overrides the policy, effectively blocking all public access.

Answer

The bucket is public because the bucket policy allows GetObject.

Answer

The bucket is public only for IPs in the 203.0.113.0/24 range.

Answer

The bucket is private because no ACLs allow public access.

Question 2

Refer to the exhibit. A security engineer reviews the AWS WAF web ACL configuration. What is the effect of this configuration?

Accepted Answer

It blocks IPs that send more than 2000 requests and allows requests containing '

Answer

It allows all traffic because the rules are misconfigured.

Answer

It blocks both SQL injection and XSS attacks.

Answer

It blocks SQL injection attacks and allows XSS attacks.

Question 3

A security engineer is troubleshooting connectivity issues between an Amazon EC2 instance in a VPC and an on-premises server over a Direct Connect virtual interface. The EC2 instance has a security group that allows outbound traffic to the on-premises CIDR block (10.0.0.0/16). The VPC has a route table entry pointing the on-premises CIDR to the virtual private gateway. The on-premises firewall shows that packets are received from the EC2 instance but responses are not reaching the instance. What is the most likely cause?

Accepted Answer

The on-premises router does not have a route pointing the VPC CIDR back to the Direct Connect interface.. The on-premises firewall logs show packets are received from the EC2 instance, but responses are not reaching it. This indicates a routing issue on the on-premises side: the on-premises router must have a route pointing the VPC CIDR back to the Direct Connect interface (virtual interface) for return traffic to be forwarded correctly. Without this return route, the on-premises server sends responses via its default route (likely the internet), which are dropped by the VPC security group or never reach the EC2 instance.

Answer

The network ACL for the subnet is blocking outbound traffic to the on-premises CIDR.

Answer

The virtual private gateway is not attached to the VPC.

Answer

The security group does not allow inbound traffic from the on-premises server.

Question 4

A financial services company runs a critical application on Amazon EC2 instances in a VPC. The application processes sensitive financial data and must meet strict compliance requirements. The security team recently discovered that an EC2 instance was compromised due to an unpatched vulnerability. The attacker used the instance's IAM role to access an S3 bucket containing customer data and exfiltrated the data. The security team needs to prevent such incidents in the future. They have implemented the following controls: 
- All EC2 instances are launched in private subnets. 
- The IAM roles used by EC2 instances follow the principle of least privilege. 
- Security groups restrict inbound and outbound traffic. 
- AWS Systems Manager Patch Manager is used to patch instances. 
- AWS CloudTrail is enabled and logs are sent to a centralized S3 bucket. 
- Amazon GuardDuty is enabled.

Despite these controls, the team is concerned about the blast radius if an instance is compromised again. Which additional measure would MOST effectively limit the blast radius of a compromised EC2 instance?

Accepted Answer

Use S3 VPC Endpoints with a bucket policy that only allows access from the VPC endpoint, and use Systems Manager Session Manager instead of SSH.. Using an S3 VPC endpoint with a bucket policy that restricts access exclusively to that endpoint ensures that compromised EC2 instances can only reach S3 through the VPC endpoint, preventing data exfiltration over the internet. Additionally, replacing SSH with Systems Manager Session Manager eliminates the need for open inbound SSH ports and provides fine-grained access control through IAM, reducing the attack surface and blast radius.

Answer

Enable VPC Flow Logs to monitor traffic to S3.

Answer

Deploy AWS WAF in front of the S3 bucket.

Answer

Create an AWS Config rule to detect S3 access from EC2 instances.

Question 5

A security engineer is designing a VPC with public and private subnets. The application servers in the private subnets need to access the internet for software updates, but must not be directly reachable from the internet. Which TWO actions satisfy these requirements?

Accepted Answer

Add a route in the private subnet's route table pointing to the NAT gateway.. A NAT gateway, when deployed in a public subnet with an associated Elastic IP and a route to an internet gateway, allows instances in private subnets to initiate outbound connections to the internet (e.g., for software updates) while preventing any unsolicited inbound connections from the internet. The private subnet's route table must include a default route (0.0.0.0/0) pointing to the NAT gateway's private IP address to forward outbound traffic through it.

Answer

Configure the private subnet's security group to allow inbound traffic from 0.0.0.0/0.

Answer

Attach an internet gateway to the private subnet's route table.

Answer

Create a VPC gateway endpoint for Amazon S3.

Question 6

A security engineer is designing a VPC with public and private subnets. The application must be able to send outbound traffic to the internet, but inbound traffic from the internet must be blocked except for a single HTTP load balancer. The application also needs to access an S3 bucket in the same AWS region. Which combination of VPC components meets these requirements? (Choose two.)

Accepted Answer

NAT Gateway in a public subnet. A NAT Gateway in a public subnet allows instances in private subnets to initiate outbound traffic to the internet (e.g., for software updates or API calls) while blocking unsolicited inbound connections. This satisfies the requirement for outbound internet access without exposing private instances directly.

Answer

S3 Interface Endpoint in the VPC

Answer

VPC Peering to a shared services VPC

Answer

Internet Gateway attached to the VPC

Question 7

A company has a VPC with a public subnet and a private subnet. An EC2 instance in the private subnet needs to download patches from the internet. The instance is associated with a security group that allows outbound HTTPS (port 443) to 0.0.0.0/0. The private subnet route table has a default route (0.0.0.0/0) pointing to a NAT Gateway in the public subnet. The NAT Gateway's security group allows inbound HTTPS from the private subnet CIDR. However, the instance cannot download patches. What is the most likely cause?

Accepted Answer

The NAT Gateway's security group is blocking outbound traffic to the internet. The NAT Gateway's security group must allow outbound traffic to the internet for the patches to be retrieved. Even though the NAT Gateway allows inbound HTTPS from the private subnet, it also needs an outbound rule permitting HTTPS traffic to 0.0.0.0/0 so that response packets from the internet can flow back through the NAT Gateway to the instance. Without this outbound rule, the NAT Gateway drops the return traffic, preventing the download.

Answer

The network ACL for the private subnet is blocking outbound traffic

Answer

The private subnet route table does not have a route to the NAT Gateway

Answer

The security group attached to the EC2 instance is blocking inbound traffic

Question 8

A company has a VPC with public and private subnets. An EC2 instance in a private subnet needs to access an S3 bucket to store logs. The security team wants to ensure that traffic does not traverse the internet. Which solution should be used? (Choose two.)

Accepted Answer

Create an S3 Gateway Endpoint in the VPC. A VPC Gateway Endpoint (option A) allows instances in a private subnet to access S3 without traversing the internet by routing traffic through AWS's internal network. This is the correct foundational component because it uses prefix lists in the route table to direct S3 traffic to the endpoint, bypassing the need for an Internet Gateway or NAT Gateway.

Answer

Attach an Internet Gateway to the VPC

Answer

Create an S3 Interface Endpoint in the VPC

Answer

Use a NAT Gateway to route the traffic to the internet

Question 9

A company uses Amazon CloudFront with an Application Load Balancer (ALB) as the origin. The security team wants to restrict access to the ALB so that it only accepts traffic from CloudFront. Which configuration should be used?

Accepted Answer

Configure the ALB security group to allow inbound traffic only from the CloudFront origin IP ranges published by AWS.. CloudFront publishes a list of its origin-facing IP address ranges, and you can restrict the ALB's security group to allow inbound traffic only from those ranges. This ensures that only CloudFront can reach the ALB directly, preventing bypass attacks. AWS provides these IP ranges in the ip-ranges.json file, which can be used to automate security group updates.

Answer

Configure the ALB to be internal and place it in a VPC with a CloudFront VPC origin.

Answer

Configure the ALB to require a specific header 'X-CloudFront-Origin' and reject requests without it.

Answer

Configure the ALB to use an IAM role that allows only CloudFront to invoke the ALB.

Question 10

A company is using AWS Direct Connect with a private virtual interface (VIF) to connect its on-premises network to a VPC. The security team wants to encrypt traffic over the Direct Connect connection. Which TWO options can be used? (Choose TWO.)

Accepted Answer

Enable MACsec on the Direct Connect connection.. MACsec (IEEE 802.1AE) provides encryption at Layer 2 (data link layer) and can be enabled directly on a Direct Connect connection. This encrypts all traffic between the on-premises router and the AWS Direct Connect endpoint without requiring any changes to higher-layer protocols, making it transparent to applications.

Answer

Use AWS KMS to encrypt the traffic.

Answer

Use AWS Certificate Manager to issue certificates for the connection.

Answer

Use SSL/TLS to encrypt the traffic between on-premises and AWS.

Question 11

Refer to the exhibit. A security engineer reviews this CloudFormation template. Which statement about the bucket's public accessibility is correct?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The flow log was created at the VPC level, not at the subnet level.. The output shows the resource ID as a VPC (vpc-xxxx), but the security engineer expected to see flow logs for a specific subnet. This indicates that the flow log was created at the VPC level, not at the subnet level. In AWS, VPC Flow Logs can be created at the VPC, subnet, or network interface level, and the resource ID in the flow log output reflects the level at which the log was configured. Since the engineer expected subnet-level logs, the most likely reason is that the flow log was created for the entire VPC instead of the specific subnet.

Answer

The flow log is not active; it shows ACTIVE, so that's not the issue.

Answer

The flow log is configured to deliver to CloudWatch, but the log group name is incorrect.

Answer

The IAM role does not have permissions to deliver logs for subnets.

Question 12

A company has an AWS Lambda function that needs to access an Amazon RDS database. The database is in a private subnet. Which configuration will allow the Lambda function to securely access the database without traversing the internet?

Accepted Answer

Configure the Lambda function to run in the same VPC as the RDS database, in the same private subnet.. Placing the Lambda function in the same VPC and the same private subnet as the RDS database allows the Lambda function to communicate with the database directly over the AWS network using private IP addresses. This configuration ensures traffic does not traverse the internet, and it leverages VPC routing and security groups for access control. Lambda functions must be configured with VPC settings to access resources in private subnets, and when both are in the same subnet, no additional gateways or peering are required.

Answer

Create a VPC peering connection between the Lambda VPC and the RDS VPC.

Answer

Place the Lambda function in a public subnet and use a NAT gateway to access the RDS database.

Answer

Use a VPC endpoint for Lambda to connect to the RDS database.

Question 13

A security engineer notices that an Amazon EC2 instance has a security group that allows inbound SSH (port 22) from 0.0.0.0/0. The instance is a bastion host. What is a more secure alternative to this configuration?

Accepted Answer

Remove the inbound SSH rule and use AWS Systems Manager Session Manager to access the instance.. AWS Systems Manager Session Manager provides secure, auditable, and keyless shell access to EC2 instances without opening any inbound ports. It uses the AWS Systems Manager agent to initiate an outbound connection to the AWS SSM endpoint over HTTPS (port 443), eliminating the need for a bastion host or any inbound SSH rule. This approach also integrates with AWS Identity and Access Management (IAM) for fine-grained access control and AWS CloudTrail for full session logging.

Answer

Change the SSH port to a non-standard port to avoid automated attacks.

Answer

Restrict the inbound SSH rule to a single IP address from the corporate network.

Answer

Replace the security group rule with a network ACL that allows SSH from 0.0.0.0/0.

Question 14

A company has a VPC with public and private subnets. The private subnets need to access the internet for software updates. Which component should be added to the VPC to enable this?

Accepted Answer

NAT gateway. (NAT gateway). A NAT gateway enables instances in a private subnet to initiate outbound traffic to the internet for tasks like software updates, while preventing inbound traffic from the internet. Option A (Internet gateway) is incorrect because it is used for public subnets to allow direct internet access. Option B (VPN connection) is used for secure connectivity to an on-premises network, not for outbound internet access. Option C (VPC peering connection) is used to connect two VPCs, not to provide internet access.

Answer

Internet gateway

Answer

VPN connection

Answer

VPC peering connection

Question 15

A company uses an AWS Transit Gateway to connect multiple VPCs and on-premises networks. A security engineer needs to ensure that traffic between VPCs is inspected by a third-party firewall appliance. Which architecture should be used?

Accepted Answer

Attach the firewall appliance to a dedicated inspection VPC and route traffic from other VPCs through the inspection VPC using transit gateway route tables.. It uses a dedicated inspection VPC as a central point for traffic inspection. By attaching the third-party firewall appliance to this inspection VPC and manipulating transit gateway route tables, you can force all inter-VPC traffic to be routed through the firewall for inspection. This architecture leverages the transit gateway's ability to route traffic between attachments based on route table entries, enabling centralized security enforcement without modifying individual VPC routing.

Answer

Configure security groups on the transit gateway to inspect traffic.

Answer

Create VPC endpoints for each VPC to route traffic through the firewall.

Answer

Use network ACLs on the transit gateway to filter traffic.