How do you protect AWS EC2 instances from security threats and unauthorised access?

a. Patch Management: Apply security patches and upgrades to EC2 instances on a regular basis to reduce vulnerabilities and protect them from known security threats.

b. Use security groups and network ACLs to manage inbound and outbound traffic to EC2 instances. Follow the concept of least privilege by restricting access to only the most necessary ports and protocols.

c. Instance Hardening: Turn off superfluous services and protocols on EC2 instances. Follow industry best practices for security configuration, such as turning off remote root login, using strong passwords, and enabling security systems (e.g. firewall etc) settings.

d. IAM Roles and Policies: Assign IAM roles to EC2 instances with only the rights required to access other AWS services. Restrict access to AWS resources using least privilege principles.

e. Monitoring and Logging: Enable AWS CloudWatch Logs and other logging techniques to track EC2 instance activity and performance. Set up alerts and notifications for strange behaviour or security incidents.

f. Data Encryption: Secure data at rest and in transit on EC2 instances. Use AWS encryption techniques, such as AWS Key Management Service (KMS), to securely manage encryption keys.

g. Perform frequent security audits and vulnerability assessments on EC2 instances with tools such as AWS Inspector. Proactively detect and fix security flaws and compliance issues.