Difference between Security Group and Network ACL in AWS

In AWS Cloud, Both the security groups and network ACLs play a important roles in managing the network traffic, but they work differently. Understanding the difference of these make us the aware of the security implementation of AWS Setup. In the article, we will disucss in detail about what are Security groups and Network ACL, their differences and troubleshooting issues much more..

The following are the difference between Security Groups and Network ACLs:

Security group like a virtual firewall. It has inbound and outbound security rules in which all inbound traffic is blocked by default in private on AWS EC2. It does not allow particular protocol no one will able to access our instances using this protocol you can stop traffic by using that rule by default everything that is denied. There are various multiple security groups on EC2 instances. We can not block a specific IP address using that security group but using the network access list. In which we edit any rule a security group with faster effect. 

Network ACL is a modifiable default network. It allows all the inbound or outbound IPv4 traffic and here we create a type of custom network all or each custom network ACL denies all inbound and outbound traffic. This network is the stateless and separate inbound and outbound rule with a default limit of 20 for both rules and starting with the lowest numbered rule. In which all subnet in VPC must be combined with network ACL one subnet to other network ACL at a time. It supports rules and deny rules and operate the subnet level.

Network ACLs evaluates the traffic that is entering or leaving the subnet in your VPC (Virtual Private Cloud). They process the rules in a sequential order, starting from the lowest numbered rules. When a packet matches the rules then it checks whether it is permitable or denied one. If the rule letting for permitting the packet then only it will be allowed. If they are match rules then the default action deny is applied. This process helps in enforcing the security polices and protect your AWS infrastructure from the unathorized access and potential threats.

The following are the differences between Network ACL and Route Table:

The following are the steps that guides you in controlling the traffic to subnets using the Network ACLs:

Step 1: Create a Network ACL

• Firstly start by creating a Network ACL in your VPC through the AWS management Console or using AWS CLI commands.

Step 2: Associate the Network ACL with Subnets

• Associate the network ACLs with the subnets where you want to control the traffic.
• You can also associate one NACL to mutliple subnets, but each subnet can only have one Network ACL assoicated with it at a time.

Step 3: Define Inbound and Outbound Rules

• Configure the inbound and outbound rules within the network ACL to permit or deny any specific types of traffic. Rules are evaluated in order, starting with the lowest numbered rules.

Step 4: Priortize Rules

• Arrange the rule in the order of priority, with the most specific rules at the top and the more general rules at the bottom facilitating its evaluation against the appropriate rules.

Step 5: Configure Rule Actions

• Specify the action whether to the traffic rule to be allowed or deny for each rule based on your security requirments. Example: you can allows the HTTP and HTTPS traffic while denying the access to specific IP addresses and protocols.
• Apply the changes to the Network ACL. The updated rules will take the effect immediately and start controlling the traffic that is coming to the associated subnets.

Network ACLs (Access Control Lists) in AWS act as a virtual firewall at the subnet level, controlling inbound and outbound traffic. They are stateless and evaluate traffic based on rules defined within them. Each subnet in a VPC can be associated with a Network ACL, allowing you to customize access control for different parts of your network infrastructure.

Network ACL rules define the permissions for traffic entering and leaving a subnet. Rules are processed in order, from the lowest to highest rule number, and the first rule that matches the traffic criteria is applied. Rules can permit or deny traffic based on IP addresses, protocols, and port numbers, providing granular control over network communication.

Network ACLs work in conjunction with other AWS services to enhance security and network management. They complement security groups by providing an additional layer of defense at the subnet level. Network ACLs also integrate with AWS CloudFormation and AWS CLI, allowing you to automate the deployment and management of network access controls within your infrastructure.

To effectively work with Network ACLs, start by understanding your network traffic requirements and security policies. Create Network ACLs and associate them with the appropriate subnets in your VPC. Define and prioritize inbound and outbound rules based on your security needs, regularly reviewing and updating them as necessary. Monitor network traffic and performance to ensure that your Network ACL configurations are effectively controlling access and meeting your security objectives.

The following are the some of the troubleshootings of Security Groups and Network ACLs:

1. Review Rules Configuration: Try on reviewing the rules that are configured in both the security groups and network ACLs. Check for any misconfigurations or conflicting rules that causing the issues.
2. Check Logging and Monitoring: Look on utilizing of AWS CloudWatch Logs and VPC Flow Logs to monitor and analyze the network traffic. It looks for any denied or dropped connections that could indicates the issues with the security groups or Network ACLs.
3. Check Associated Resources: Confirmation of the security groups and network ACLs are correctly associated with the intended resources such as EC2 instances or subnets for ensuring the changes that made for security groups or NACLs that are properly appling to associated resources.

What is a Network ACL in AWS?

It is virtual firewall that helps in controlling the traffic at the subnet level in the AWS Cloud.

How do I manage the Network ACL using Terraform?

By defining and provisioning the terraform network ACL rules within your AWS infrastructure with terraform scripts you can manage the Network ACLs.

Can I Create a Network ACLs with AWS Cloudformation?

Yes, You can define the Network ACL resources in an AWS CloudFormation template for the automated deployments.

What is the defaulat Network ACL in AWS?

The default Network ACL allows all the inbound and outbound traffic by default until the customized rules are applied.