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My experience with network security in the cloud is foundational to my role as a Cloud Security Engineer. I've designed and implemented secure network architectures across AWS and Azure, focusing on segmentation, access control, and robust perimeter defenses using Virtual Private Clouds (VPCs), Virtual Networks (VNets), and various firewall solutions.
In AWS, I've extensively used VPCs to create isolated networks for different application environments (development, staging, production) or business units. Within each VPC, I always segment further using subnets: public subnets for internet-facing resources like load balancers and private subnets for application servers and databases. I enforce strict traffic control using a combination of Security Groups and Network Access Control Lists (NACLs). Security Groups are stateful and applied to instances, allowing me to specify granular inbound/outbound rules like "allow SSH from bastion host IP only" or "allow HTTP/S from load balancer Security Group." NACLs, which are stateless and applied at the subnet level, provide an additional layer of defense, blocking traffic at a broader stroke, such as denying all traffic from known malicious IP ranges to an entire subnet.
I've also implemented secure connectivity for hybrid environments using AWS Direct Connect or VPN Gateways. For example, I configured a Site-to-Site VPN connection between an on-premises data center and an AWS VPC, ensuring all traffic was encrypted in transit. For internal VPC-to-VPC communication, especially in multi-account setups, I use AWS Transit Gateway. This centralizes network connectivity, simplifying routing and allowing me to apply centralized network security policies. For instance, I routed all inter-VPC traffic through a 'security VPC' where we deployed a third-party firewall (like Palo Alto Networks VM-Series) as a virtual appliance, inspecting and filtering all north-south and east-west traffic before it reached its destination. This provided advanced threat protection and deep packet inspection beyond native AWS capabilities.
In Azure, the equivalent is Azure Virtual Networks (VNets). I deploy VNets for logical isolation, similar to VPCs. Within VNets, I use subnets and Azure Network Security Groups (NSGs) for traffic filtering. NSGs are similar to AWS Security Groups, allowing me to define rules for inbound and outbound traffic to and from network interfaces or subnets. I often combine NSGs with Application Security Groups (ASGs), which let me group VMs logically by application tier (e.g., web servers, database servers) and apply NSG rules to these groups, making policy management more intuitive. For example, I might have an ASG for web servers and an ASG for database servers, and an NSG rule would then state, "allow traffic from WebServer-ASG to Database-ASG on port 1433."
For advanced threat protection in Azure, I've deployed Azure Firewall, which is a stateful, managed firewall as a service. It provides centralized network security for VNet environments, offering features like FQDN filtering, threat intelligence-based filtering, and network rule collections. I used Azure Firewall to protect the perimeter of our production VNet, allowing only necessary ports and protocols from the internet and filtering outbound traffic to prevent data exfiltration. I've also implemented Web Application Firewalls (WAFs) like AWS WAF or Azure Application Gateway with WAF enabled to protect web applications from common web exploits such as SQL injection and cross-site scripting. My consistent focus is to design networks with defense-in-depth, segmenting traffic, applying least privilege to network access, and actively monitoring flow logs for anomalous activity.