CompTIA SY0-701 Online Access

A diagram of a computer AI-generated content may be incorrect.

Step 1: Understand Requirements & Security Principles

Requirements:

Customer-facing payment application (PCI DSS compliance applies)

Hosted on third-party cloud (e.g., AWS)

Must segment public-facing and internal resources

Needs to be scalable and resilient

Must have strong security controls

Step 2: Design the High-Level Network Layout

Core Components:

VPC (Virtual Private Cloud): Isolates your environment from other tenants in the cloud.

Subnets:

Public subnet: For resources that must communicate with the internet.

Private subnet: For internal resources, NOT directly exposed to the internet.

Step 3: Place Resources in Appropriate Subnets

Public Subnet:

Internet-facing Load Balancer (LB): Distributes traffic to application servers.

Web Application Firewall (WAF): Protects against web exploits.

Autoscaling Instances: EC2 (or VM) servers running your web front-end, automatically scaling as traffic grows.

Private Subnet:

Application servers: Back-end logic, not exposed to internet directly.

Database: Sensitive data storage, only accessible by application servers.

Internal Load Balancer: Manages traffic among app servers.

WAF: Can be used internally as well for defense-in-depth.

Step 4: Add Connectivity and Security Controls

Internet Gateway: Allows resources in public subnet to communicate with the internet.

NAT Gateway: Allows outbound internet traffic from private subnet without exposing private IPs.

Security Groups: Firewalls at the instance level; allow only necessary traffic (e.g., LB to web server, web server to DB).

Network ACLs: Subnet-level firewalls for additional control.

Step 5: Network Diagram Explanation (Based on Your Images)

Public Subnet (Top Layer)

Load Balancer

Accepts HTTPS traffic from customers.

Sends only necessary HTTP/HTTPS to web servers in public subnet.

WAF (Web Application Firewall)

Sits in front of Load Balancer.

Filters malicious requests (SQLi, XSS, etc.).

Autoscaling Group

Multiple web servers for redundancy and scalability.

Placed in public subnet to respond to traffic spikes.

Private Subnet (Bottom Layer)

Application Servers

Receive requests from public subnet’s load balancer.

Not directly exposed to the internet.

Database

Only accessible from application servers, never public.

Security groups restrict all inbound traffic except from app servers.

Internal Load Balancer

Balances requests to application servers.

Step 6: Flow of Data (Step-by-Step)

Client -> Internet Gateway -> WAF -> Load Balancer (Public Subnet):Customers initiate connections to your app over the internet.

Load Balancer -> Autoscaling Web Servers (Public Subnet):Load balancer routes requests to available web servers.

Web Servers -> Application Logic (Private Subnet):Web servers pass necessary requests to the internal application servers.

App Servers -> Database (Private Subnet):Application servers query/update customer payment data in the database.

Outbound (NAT Gateway):App servers may need to access updates or external APIs—use NAT Gateway for secure outbound connections.

Step 7: Security Best Practices

Security Groups: Only allow necessary ports (e.g., 443 for HTTPS to LB, 3306 for MySQL between app server and DB).

Network ACLs: Add another layer of subnet-level restrictions.

Encryption: Use HTTPS for all external connections, encrypt data at rest and in transit (TLS, disk encryption).

IAM Roles/Policies: Principle of least privilege for accessing resources.

Monitoring/Logging: Enable VPC flow logs, cloud service logs, and application logging.

Patch Management: Automate patching for OS and applications.

Backups: Regular, secure backups of critical data.

Step 8: Compliance Considerations

For payment applications (PCI DSS):

Isolate cardholder data environment (CDE).

Strong access controls (multi-factor authentication, role separation).

Regular vulnerability assessments and penetration testing.

Retain logs for auditing.

Step 9: Draw the Architecture (Summary)

Internet Gateway: Allows inbound/outbound internet access.

Public Subnet: WAF, Load Balancer, Autoscaling group.

Private Subnet: App servers, DB, internal LB.

NAT Gateway: Outbound access for private resources.

Security Groups/ACLs: Control all traffic flows.

Monitoring/Logging: Enabled at all levels.

Bonus: Sample Security Group Rules

Web Server (Public Subnet):

Inbound: 443 (HTTPS) from Internet

Outbound: 80/443 to App Servers

App Server (Private Subnet):

Inbound: 80/443 from Web Servers

Outbound: 3306 (MySQL) to Database

Database (Private Subnet):

Inbound: 3306 from App Servers

Outbound: None (unless replication required)

References to Security+ Domains

1.0 General Security Concepts: Principle of least privilege, defense in depth.

2.0 Threats, Vulnerabilities, Mitigations: WAF, segmentation, patching.

3.0 Security Architecture: Network segmentation, secure design.

4.0 Security Operations: Monitoring, logging, response.

5.0 Security Program Management: Compliance, policy.

An Access Control List (ACL) is a technical mechanism used to explicitly define permissions for files, folders, or other resources. ACLs specify which users or system processes are granted access to objects and what operations are allowed on given objects. This allows the administrator to centrally and granularly manage file permissions for a group or team.

Mitigate is the risk management strategy that involves reducing the likelihood or impact of a risk. If a legacy application is critical to business operations and there are preventative controls that are not yet implemented, the enterprise should adopt the mitigate strategy first to address the existing vulnerabilities and gaps in the application. This could involve applying patches, updates, or configuration changes to the application, or adding additional layers of security controls around the application. Accept, transfer, and avoid are other risk management strategies, but they are not the best options for this scenario. Accept means acknowledging the risk and accepting the consequences without taking any action. Transfer means shifting the risk to a third party, such as an insurance company or a vendor. Avoid means eliminating the risk by removing the source or changing the process. These strategies may not be feasible or desirable for a legacy application that is critical to business operations and has no preventative controls in place. References: CompTIA Security+ Study Guide: Exam SY0-701, 9th Edition, page 1221; A Risk-Based Framework for Legacy System Migration and Deprecation2

Arace conditionoccurs whentwo or more processes attempt to access and modify a shared resource simultaneously, leading to unintended behavior. In this scenario, the attacker was able to modify a temporary fieldbefore the SQL update completed, indicating atime-of-check to time-of-use (TOCTOU) vulnerability, which is a type of race condition.

Memory injection (B)refers to inserting malicious code into a running process’s memory, but that isnotwhat is happening here.

Malicious update (C)is too broad and does not specifically describe this scenario.

Side loading (D)is a technique where malicious software is loaded via a trusted application, unrelated to this case.