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What Is EC2? Key Concepts
What Is EC2? Key Concepts EC2 (Elastic Compute Cloud) gives you virtual servers on AWS. Each server is an instance . AMI : the starting image (operating system). Key pair : the SSH key to log in. Security group : the firewall for the instance. Most EC2 breaches are on the customer side: an open port
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What it is
EC2 (Elastic Compute Cloud) gives you virtual servers on AWS. Each server is an instance.
Key terms
AMI: the starting image (operating system).
Key pair: the SSH key to log in.
Security group: the firewall for the instance.
Why it matters for security
Most EC2 breaches are on the customer side: an open port, a leaked key or a server not updated.
Common mistake
Launching a server on day one of a new account.
First turn on MFA for the root user and set a billing alert in AWS Budgets.
| Term | What it is | Example / notes |
|---|---|---|
| Instance | A virtual server | i-0abc123def4567890 |
| AMI (Amazon Machine Image) | Template with OS + software used to launch instances | Amazon Linux 2023, Ubuntu 24.04, CentOS Stream 9, your own… |
| Instance type | Hardware size: vCPU, RAM, network | t3.micro (2 vCPU, 1 GiB), t3.medium (2 vCPU, 4 GiB) |
| Key pair | Public/private key used for SSH login instead of a password | AWS keeps public key; you download mykey.pem once |
| Security group (SG) | Stateful virtual firewall at instance level | Allow TCP 22 from My IP, TCP 80/443 from 0.0.0.0/0 |
Learn more in the lesson: 4.1 What Is EC2? Key Concepts