Security Group: A Security Group acts as a virtual firewall for an Amazon EC2 instance or a set of instances.
It controls inbound and outbound traffic for instances in the same VPC. It operates at the instance level, meaning the rules apply to every instance associated with the Security Group.
The rules in a Security Group include allowing specific IP addresses or ranges, port ranges, and protocols. It can be associated with multiple instances, and instances can be associated with multiple security groups.
Security Groups are stateful, meaning if an inbound rule allows traffic, the response traffic is automatically allowed, even if no specific rule has been defined for it.
Network Access Control List (NACL): A NACL is an optional layer of security for a subnet in a VPC. It controls inbound and outbound traffic at the subnet level. It operates on a rule basis, where a rule can be defined to allow or deny traffic based on IP, port, and protocol.
Each subnet in a VPC must be associated with a NACL, and a NACL can be associated with multiple subnets. NACLs are stateless, meaning if an inbound rule allows traffic, the response traffic is not automatically allowed. NACLs are processed before Security Groups, meaning if a rule explicitly denies traffic in a NACL, it won't be allowed even if a Security Group allows it.
Application in AWS Cloud Infrastructure: Security Groups and NACLs can be applied in AWS cloud infrastructure to control the traffic flow and enhance security. Security Groups can be used to define access rules at the instance level, allowing only necessary traffic to and from instances based on their IP, port, and protocol. It is often used to protect instances and services running in the VPC.
NACLs, on the other hand, provide an additional layer of control at the subnet level. It allows more granular control over traffic entering or leaving specific subnets.
By carefully configuring Security Groups and NACLs, organizations can enforce fine-grained access control, prevent unauthorized access, and minimize potential attack surfaces in their AWS cloud infrastructure.
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