Scenario 6: EC2 Instance Exhibiting Signs of Compromise or Suspicious Activity

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Problem:

• The EC2 instance is showing unusual outbound traffic and running unexpected processes.
  
  

• There is a suspicion that the instance has been compromised by malware or an unauthorized user.
  
  

• Sensitive data and other resources may be at risk.
  
  

Step-by-Step Troubleshooting:

1. Examine CloudTrail and VPC Flow Logs:
   
   

   • Review CloudTrail logs for suspicious API activity such as unexpected instance starts, stops, or IAM changes.
     
     

   • Look for unusual data transfer patterns, especially large outbound traffic to unknown IP addresses.
     
     

   • Identify any unexpected changes to instance configurations, including security group or key pair modifications.
     
     

   • Use VPC Flow Logs to detect unexpected network connections, especially outbound connections to unfamiliar IP ranges or ports.
     
     

2. Review Instance Logs:
   
   

   • Check system logs for signs of unauthorized access, such as unknown login attempts or successful logins from unexpected IPs.
     
     

   • Look at application logs for unexpected command execution or errors linked to abnormal activity.
     
     

   • Search for indicators of malware, such as files in suspicious locations, unknown running processes, or changes in startup scripts.
     
     

   • Identify any changes to scheduled tasks or crontab entries.
     
     

3. Isolate the Instance:
   
   

   • Modify the instance’s security group to block all outbound traffic except for management access.
     
     

   • Disconnect it from critical systems and databases to prevent lateral movement.
     
     

   • Create snapshots of the instance and EBS volumes for forensic analysis before making changes.
     
     

   • Stop any processes that are clearly malicious or unauthorized to limit further damage.
     
     

4. Inspect IAM Roles and Credentials:
   
   

   • Review the IAM role attached to the instance and ensure it only has the minimum privileges required.
     
     

   • Check if any IAM credentials were stored or exposed on the instance and rotate them immediately.
     
     

   • Audit recent IAM activity for signs of privilege escalation or the creation of new users or policies.
     
     

   • Disable or remove any unused IAM roles or keys associated with the instance.
     
     

5. Plan Remediation and Recovery:
   
   

   • If compromise is confirmed, terminate the affected instance to prevent further damage.
     
     

   • Perform a root cause analysis to determine how the compromise occurred.
     
     

   • Rebuild the instance using a known secure and updated AMI.
     
     

   • Apply patches and ensure all software and dependencies are up to date.
     
     

   • Implement additional security measures such as intrusion detection systems and enhanced logging.
     
     

   • Review and improve incident response plans and conduct a post-incident review.
     
     

Key AWS Terms:

• CloudTrail: Service that records API calls made in an AWS account.
  
  

• VPC Flow Logs: Network traffic logs for VPC interfaces, useful for detecting suspicious traffic.
  
  

• IAM Role: Permissions assigned to AWS services, which must follow the principle of least privilege.
  
  

• Security Group: Instance-level firewall used to control network access.
  
  

• AMI: Amazon Machine Image used to launch EC2 instances.
  
  

Interview Insight:

• When an EC2 instance shows signs of compromise, I immediately isolate it by restricting its security group.
  
  

• I review CloudTrail and VPC Flow Logs to identify how the breach happened and what actions were taken by the attacker.
  
  

• I ensure IAM credentials are rotated and only least-privileged roles are used.
  
  

• After confirming the issue, I terminate the compromised instance, conduct a full analysis, and rebuild with tightened security controls.