Security best practices for Windows instances - Amazon Elastic Compute Cloud

Security best practices for Windows instances

We recommend that you follow these security best practices for your Windows instances.

High-level security best practices

You should adhere to the following high-level security best practices for your Windows instances:

  • Least access – Grant access only to systems and locations that are trusted and expected. This applies to all Microsoft products such as Active Directory, Microsoft business productivity servers, and infrastructure services such as Remote Desktop Services, reverse proxy servers, IIS web servers,and more. Use AWS capabilities such as Amazon EC2 instance security groups, network access control lists (ACLs), and Amazon VPC public/private subnets to layer security across multiple locations in an architecture. Within a Windows instance, customers can use Windows Firewall to further layer a defense-in-depth strategy within their deployment. Install only the OS components and applications that are necessary for the system to function as designed. Configure infrastructure services such as IIS to run under service accounts, or to use features such as application pool identities to access resources locally and remotely across your infrastructure.

  • Least privilege – Determine the minimum set of privileges that instances and accounts need in order to perform their functions. Restrict these servers and users to only allow these defined permissions. Use techniques such as Role Based Access Controls to reduce the surface area of administrative accounts, and create the most limited roles to accomplish a task. Use OS features such as Encrypting File System (EFS) within NTFS to encrypt sensitive data at rest, and control application and user access to it.

  • Configuration management – Create a baseline server configuration that incorporates up-to-date security patches and host-based protection suites that include anti-virus, anti-malware, intrusion detection/prevention, and file integrity monitoring. Assess each server against the current recorded baseline to identify and flag any deviations. Ensure each server is configured to generate and securely store appropriate log and audit data.

  • Change management – Create processes to control changes to server configuration baselines and work toward fully automated change processes. Also, leverage Just Enough Administration (JEA) with Windows PowerShell DSC to limit administrative access to the minimum required functions.

  • Patch management – Implement processes that regularly patch, update, and secure the operating system and applications on your EC2 instances.

  • Audit logs – Audit access and all changes to Amazon EC2 instances to verify server integrity and ensure only authorized changes are made. Leverage features such as Enhanced Logging for IIS to enhance default logging capabilities. AWS capabilities such as VPC Flow Logs and AWS CloudTrail are also available to audit network access, including allowed/denied requests and API calls, respectively.

Update management

To ensure the best results when you run Windows Server on Amazon EC2, we recommend that you implement the following best practices:

For information about how to upgrade or migrate a Windows instance to a newer version of Windows Server, see Upgrade an Amazon EC2 Windows instance to a newer version of Windows Server.

Configure Windows Update

By default, instances that are launched from AWS Windows Server AMIs don't receive updates through Windows Update.

Update Windows drivers

Maintain the latest drivers on all Windows EC2 instances to ensure that the latest issue fixes and performance enhancements are applied across your fleet. Depending on your instance type, you should update the AWS PV, Amazon ENA, and AWS NVMe drivers.

Launch instances using the latest Windows AMIs

AWS releases new Windows AMIs each month, which contain the latest OS patches, drivers, and launch agents. You should leverage the latest AMI when you launch new instances or when you build your own custom images.

Test system/application performance before migration

Migrating enterprise applications to AWS can involve many variables and configurations. Always performance test the EC2 solution to ensure that:

  • Instance types are properly configured, including instance size, enhanced networking, and tenancy (shared or dedicated).

  • Instance topology is appropriate for the workload and leverages high-performance features when necessary, such as dedicated tenancy, placement groups, instance store volumes, and bare metal.

Update launch agents

Update to the latest EC2Launch v2 agent to ensure that the latest enhancements are applied across your fleet. For more information, see Migrate to EC2Launch v2.

If you have a mixed fleet, or if you want to continue to use the EC2Launch (Windows Server 2016 and 2019) or EC2 Config (legacy OS only) agents, update to the latest versions of the respective agents.

Automatic updates are supported on the following combinations of Windows Server version and launch agents. You can opt in to automatic updates in the SSM Quick Setup Host Management console under Amazon EC2 Launch Agents.

Windows Version EC2Launch v1 EC2Launch v2

Configuration management

Amazon Machine Images (AMIs) provide an initial configuration for an Amazon EC2 instance, which includes the Windows OS and optional customer-specific customizations, such as applications and security controls. Create an AMI catalog containing customized security configuration baselines to ensure that all Windows instances are launched with standard security controls. Security baselines can be baked into an AMI, bootstrapped dynamically when an EC2 instance is launched, or packaged as a product for uniform distribution through AWS Service Catalog portfolios. For more information on securing an AMI, see Best Practices for Building an AMI.

Each Amazon EC2 instance should adhere to organizational security standards. Do not install any Windows roles and features that are not required, and do install software to protect against malicious code (antivirus, antimalware, exploit mitigation), monitor host-integrity, and perform intrusion detection. Configure security software to monitor and maintain OS security settings, protect the integrity of critical OS files, and alert on deviations from the security baseline. Consider implementing recommended security configuration benchmarks published by Microsoft, the Center for Internet Security (CIS), or the National Institute of Standards and Technology (NIST). Consider using other Microsoft tools for particular application servers, such as the Best Practice Analyzer for SQL Server.

AWS customers can also run Amazon Inspector assessments to improve the security and compliance of applications deployed on Amazon EC2 instances. Amazon Inspector automatically assesses applications for vulnerabilities or deviations from best practices and includes a knowledge base of hundreds of rules mapped to common security compliance standards (for example, PCI DSS) and vulnerability definitions. Examples of built-in rules include checking if remote root login is enabled, or if vulnerable software versions are installed. These rules are regularly updated by AWS security researchers.

When securing Windows instances, we recommend that you implement Active Directory Domain Services to enable a scalable, secure, and manageable infrastructure for distributed locations. Additionally, after launching instances from the Amazon EC2 console or by using an Amazon EC2 provisioning tool, such as AWS CloudFormation, it is good practice to utilize native OS features, such as Microsoft Windows PowerShell DSC to maintain configuration state in the event that configuration drift occurs.

Change management

After initial security baselines are applied to Amazon EC2 instances at launch, control ongoing Amazon EC2 changes to maintain the security of your virtual machines. Establish a change management process to authorize and incorporate changes to AWS resources (such as security groups, route tables, and network ACLs) as well as to OS and application configurations (such as Windows or application patching, software upgrades, or configuration file updates).

AWS provides several tools to help manage changes to AWS resources, including AWS CloudTrail, AWS Config, AWS CloudFormation, AWS Elastic Beanstalk, and AWS OpsWorks, and management packs for Systems Center Operations Manager and System Center Virtual Machine Manager. Note that Microsoft releases Windows patches the second Tuesday of each month (or as needed) and AWS updates all Windows AMIs managed by AWS within five days after Microsoft releases a patch. Therefore it is important to continually patch all baseline AMIs, update AWS CloudFormation templates and Auto Scaling group configurations with the latest AMI IDs, and implement tools to automate running instance patch management.

Microsoft provides several options for managing Windows OS and application changes. SCCM, for example, provides full lifecycle coverage of environment modifications. Select tools that address business requirements and control how changes will affect application SLAs, capacity, security, and disaster recovery procedures. Avoid manual changes and instead leverage automated configuration management software or command line tools such as the EC2 Run Command or Windows PowerShell to implement scripted, repeatable change processes. To assist with this requirement, use bastion hosts with enhanced logging for all interactions with your Windows instances to ensure that all events and tasks are automatically recorded.

Audit and accountability for Amazon EC2 Windows instances

AWS CloudTrail, AWS Config, and AWS Config Rules provide audit and change tracking features for auditing AWS resource changes. Configure Windows event logs to send local log files to a centralized log management system to preserve log data for security and operational behavior analysis. Microsoft System Center Operations Manager (SCOM) aggregates information about Microsoft applications deployed to Windows instances and applies preconfigured and custom rulesets based on application roles and services. System Center Management Packs build on SCOM to provide application-specific monitoring and configuration guidance. These Management Packs support Windows Server Active Directory, SharePoint Server 2013, Exchange Server 2013, Lync Server 2013, SQL Server 2014, and many more servers and technologies.

In addition to Microsoft systems management tools, customers can use Amazon CloudWatch to monitor instance CPU utilization, disk performance, network I/O, and perform host and instance status checks. The EC2Config, EC2Launch, and EC2Launch v2 launch agents provide access to additional, advanced features for Windows instances. For example, they can export Windows system, security, application, and Internet Information Services (IIS) logs to CloudWatch Logs which can then be integrated with Amazon CloudWatch metrics and alarms. Customers can also create scripts that export Windows performance counters to Amazon CloudWatch custom metrics.