3.2.1. EC2 Instance Security (Patching, Hardening, Instance Profiles)

First Principle: Securing EC2 instances involves regular patching, hardening the operating system, and assigning IAM roles via instance profiles for least privilege access to AWS services.

Amazon EC2 instances are virtual servers that you control at the operating system level. This gives you flexibility but also places significant security responsibilities on you.

Key EC2 Instance Security Best Practices:

• Patch Management: Regularly apply security updates and patches to the guest operating system and installed applications (AWS Systems Manager Patch Manager).
• OS Hardening: Configure the operating system securely by:
  • Disabling unnecessary services and ports.
  • Removing default accounts and changing default passwords.
  • Implementing strong password policies.
  • Configuring host-based firewalls (e.g., iptables for Linux).
  • Regularly reviewing log files for suspicious activity.
• IAM Roles via Instance Profiles:
  • Purpose: The most secure way for applications running on EC2 instances to access other AWS services (e.g., S3, DynamoDB).
  • Mechanism: An [IAM role](https://docs.aws.amazon.com/IAM/latest/UserG uide/id_roles.html) is attached to the EC2 instance via an instance profile. The application assumes this role to get temporary credentials.
  • Benefits: Avoids hardcoding credentials in application code, ensures temporary credentials, and supports the Principle of Least Privilege.
• Network Access: Control inbound/outbound traffic using Security Groups and Network ACLs. Use Systems Manager Session Manager for secure remote access without opening SSH ports.

Scenario: You are responsible for securing a fleet of EC2 instances that host a critical application. You need to ensure these instances are regularly updated, have secure operating system configurations, and can access Amazon S3 without hardcoding credentials.

Reflection Question: How does securing EC2 instances (e.g., through regular patching, OS hardening, and assigning IAM roles via instance profiles) fundamentally protect your application's execution environment by ensuring least privilege access to AWS services and mitigating vulnerabilities?