Disablevpcclassiclink remediation

​

Event Information

• The DisableVpcClassicLink event in AWS for EC2 refers to the action of disabling ClassicLink for a specific Amazon EC2 instance within a Virtual Private Cloud (VPC).
• ClassicLink is a feature that allows EC2 instances in a VPC to communicate with instances in the EC2-Classic platform using private IP addresses. Disabling ClassicLink for an instance means that it will no longer be able to communicate with EC2-Classic instances.
• This event can be triggered manually by an administrator or through automation scripts to control the network connectivity options for EC2 instances within a VPC.

​

Examples

• Loss of connectivity: Disabling VPC ClassicLink for EC2 instances can result in loss of connectivity between the instances and ClassicLink-enabled resources in the ClassicLink-enabled VPC. This can impact the ability to access resources and services that rely on this connectivity.
• Limited network access: Disabling VPC ClassicLink can restrict network access for EC2 instances, as they will no longer be able to communicate with ClassicLink-enabled resources in the ClassicLink-enabled VPC. This can impact the functionality of applications or services that rely on this communication.
• Reduced security controls: Disabling VPC ClassicLink can lead to reduced security controls for EC2 instances, as they will no longer benefit from the security groups and network ACLs associated with the ClassicLink-enabled VPC. This can increase the risk of unauthorized access or compromise of the instances.

​

Remediation

​

Using Console

1. Example 1: Unauthorized Access to AWS EC2 Instance
   • Step 1: Identify the unauthorized access event in the AWS CloudTrail logs or AWS Security Hub.
   • Step 2: Determine the source IP address or user account associated with the unauthorized access.
   • Step 3: Disable or remove the compromised user account or IAM role from the EC2 instance’s security group or IAM policies.
   • Step 4: Change the SSH key pair associated with the EC2 instance to prevent further unauthorized access.
   • Step 5: Enable AWS CloudTrail logging and configure alerts to be notified of any future unauthorized access attempts.
2. Example 2: High CPU Utilization on AWS EC2 Instance
   • Step 1: Monitor the CPU utilization of the EC2 instance using Amazon CloudWatch metrics.
   • Step 2: Identify the process or application causing the high CPU utilization.
   • Step 3: Optimize the application or process to reduce CPU usage, such as optimizing code, improving database queries, or scaling horizontally.
   • Step 4: Consider upgrading the EC2 instance type to a higher CPU capacity if the current instance is consistently under high CPU load.
   • Step 5: Set up CloudWatch alarms to notify you when CPU utilization exceeds a certain threshold in the future.
3. Example 3: Unencrypted EBS Volume in AWS EC2 Instance
   • Step 1: Identify the unencrypted EBS volume using AWS Config or AWS Security Hub.
   • Step 2: Create a snapshot of the unencrypted EBS volume as a backup.
   • Step 3: Copy the data from the unencrypted EBS volume to a new encrypted EBS volume.
   • Step 4: Attach the new encrypted EBS volume to the EC2 instance.
   • Step 5: Update any references or configurations that point to the old unencrypted EBS volume to use the new encrypted EBS volume.

​

Using CLI

1. Ensure that all EC2 instances are using the latest Amazon Machine Images (AMIs) by regularly checking for updates and patching any vulnerabilities. Use the following AWS CLI commands:
   • To list all EC2 instances: aws ec2 describe-instances
   • To get the latest AMI ID for a specific instance type: aws ec2 describe-images --owners amazon --filters "Name=name,Values=amzn2-ami-hvm-2.0.????????-x86_64-gp2" --query 'Images[*].[ImageId,CreationDate]' --output text | sort -k2 -r | head -n 1
   • To update an instance with the latest AMI: aws ec2 create-image --instance-id <instance-id> --name "My server" --description "An AMI for my server" --no-reboot
2. Implement security groups and network ACLs to restrict inbound and outbound traffic to only necessary ports and protocols. Use the following AWS CLI commands:
   • To create a security group: aws ec2 create-security-group --group-name MySecurityGroup --description "My security group"
   • To add inbound rules to a security group: aws ec2 authorize-security-group-ingress --group-id <security-group-id> --protocol tcp --port <port-number> --cidr <ip-range>
   • To add outbound rules to a security group: aws ec2 authorize-security-group-egress --group-id <security-group-id> --protocol tcp --port <port-number> --cidr <ip-range>
3. Enable AWS CloudTrail to monitor and log all API activity within your AWS account. Use the following AWS CLI commands:
   • To create a new CloudTrail trail: aws cloudtrail create-trail --name MyTrail --s3-bucket-name <bucket-name>
   • To enable CloudTrail for all regions: aws cloudtrail update-trail --name MyTrail --is-multi-region-trail
   • To start logging API activity: aws cloudtrail start-logging --name MyTrail

​

Using Python

1. Enforce encryption for EBS volumes:
   • Use the AWS SDK for Python (Boto3) to identify unencrypted EBS volumes.
   • Create a Python script that iterates through all EC2 instances and their attached volumes.
   • For each unencrypted volume, use the create_snapshot method to create a snapshot of the volume.
   • Use the copy_snapshot method to copy the snapshot and enable encryption during the copy process.
   • Once the encrypted snapshot is created, use the create_volume method to create a new encrypted volume.
   • Finally, detach the unencrypted volume and attach the newly created encrypted volume to the instance.
2. Enable VPC flow logs:
   • Use Boto3 to check if VPC flow logs are enabled for each VPC.
   • Create a Python script that iterates through all VPCs and checks if flow logs are enabled.
   • If flow logs are not enabled, use the create_flow_logs method to enable them.
   • Specify the desired configuration, such as the destination S3 bucket, IAM role, and log format.
3. Enable AWS Config:
   • Use Boto3 to check if AWS Config is enabled for the AWS account.
   • Create a Python script that checks the status of AWS Config.
   • If AWS Config is not enabled, use the put_configuration_recorder and put_delivery_channel methods to enable it.
   • Specify the desired configuration, such as the S3 bucket for storing configuration history and the IAM role for delivery channel.