​
Event Information

  • The CreateNetworkAclEntry event in AWS for EC2 refers to the action of creating a new entry in a network access control list (ACL) for an EC2 instance.
  • Network ACLs act as a virtual firewall for controlling inbound and outbound traffic at the subnet level in AWS.
  • This event signifies the addition of a new rule to the network ACL, specifying the allowed or denied traffic based on criteria such as IP addresses, protocols, and ports.

​
Examples

  • Allowing unrestricted inbound or outbound traffic by specifying a rule with a source or destination IP range of 0.0.0.0/0 can impact security. This can potentially expose the EC2 instance to unauthorized access or allow it to communicate with malicious entities.
  • Granting overly permissive access by specifying a rule with a protocol of “all” or a wide range of ports (e.g., 0-65535) can impact security. This can increase the attack surface and make it easier for attackers to exploit vulnerabilities.
  • Allowing traffic from untrusted or unverified sources by specifying a rule with a source IP range that includes IP addresses or CIDR blocks outside of trusted networks can impact security. This can introduce the risk of unauthorized access or malicious activities.

​
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 or RDP password associated with the EC2 instance.
    • Step 5: Enable AWS CloudTrail logging and configure alerts to detect and respond to similar unauthorized access attempts in the future.

  2. Example 2: Unusual Network Traffic from AWS EC2 Instance

    • Step 1: Analyze the network traffic logs or VPC Flow Logs to identify the unusual traffic patterns.
    • Step 2: Determine the source and destination IP addresses, ports, and protocols involved in the unusual traffic.
    • Step 3: Review the security group rules associated with the EC2 instance and ensure that only necessary ports and protocols are allowed.
    • Step 4: If the unusual traffic is identified as malicious, block the source IP address using AWS Network ACLs or Security Groups.
    • Step 5: Implement network traffic monitoring and anomaly detection mechanisms to proactively identify and respond to similar incidents.

  3. Example 3: High CPU Utilization on AWS EC2 Instance

    • Step 1: Monitor the CPU utilization metrics of the EC2 instance using Amazon CloudWatch.
    • Step 2: Identify the processes or applications causing the high CPU utilization.
    • Step 3: Optimize the application or workload running on the EC2 instance 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 workload demands it.
    • Step 5: Set up CloudWatch alarms to notify and trigger automated actions when CPU utilization exceeds certain thresholds.

​
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> --is-multi-region-trail
    • To start logging API activity for the trail: aws cloudtrail start-logging --name MyTrail
    • To configure CloudTrail to log all management events: aws cloudtrail put-event-selectors --trail-name MyTrail --event-selectors '[{"ReadWriteType": "All", "IncludeManagementEvents": true}]'

​
Using Python

To remediate the issues mentioned in the previous response for AWS EC2 using Python, you can use the following approaches:

  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.

Please note that the provided code snippets are simplified examples, and you may need to modify them based on your specific requirements and environment setup.