Security Groups

Question 1

Security Groups

Answer 1

Fundamental of network security in AWS

They control how traffic is allowed into or out of the EC2 instances

Only contain allow rules

Can reference by IP or by security group

Question 2

Security groups part 2

Answer 2

Act as a firewall on EC2 instances

They regulate:
- Access to Ports
- Authorized IP ranges - IPv4 and IPv6
- Control of inbound network (from other to the instance)
- Control of outbound network (from the instance to other)

Example:
Type | Protocol | Port Range | Source | Description
HTTP | TCP | 80 | 0.0.0.0/0 / test http page
SSH | TCP | 22 | 122.149.196.85/32 |
Custom TCP Rule | TCP | 4567 | 0.0.0.0/0 | java app

Question 3

Security Groups = Good to know

Answer 3

Can be attached to multiple instances

Locked down to a region / VPC combination (if you switch another region or create another VPC you have to create a new Security Group)

Lives outside the EC2 - if traffic is blocked the EC2 instance won’t see it

It’s good to maintain one separate security group for SSH access

If your application is not accessible (time out), then it’s a security group issue

If your application gives a “connection refused” error, then it’s an application error or it’s not launched

All inbound traffic is blocked by default

All outbound traffic is authorized by default

Question 4

Classic Ports

Answer 4

22 = SSH (Secure Shell) - log into a Linux instance

21 = FTP (File Transfer Protocol) - upload files into a file share

22 = SFTP (Secure File Transfer Protocol) - upload files using SSH

80 = HTTP - access unsecured websites

443 = HTTPS - access secured websites

3389 = RDP (Remote Desktop Protocol) - log into a Windows instance