5 Best Practices to Secure AWS Resources

Originally published by CrowdStrike.

Organizations are increasingly turning to cloud computing for IT agility, resilience and scalability. Amazon Web Services (AWS) stands at the forefront of this digital transformation, offering a robust, flexible and cost-effective platform that helps businesses drive growth and innovation.

However, as organizations migrate to the cloud, they face a complex and growing threat landscape of sophisticated and cloud-conscious threat actors. Organizations with ambitious digital transformation strategies must be prepared to address these security challenges from Day One. The potential threat of compromise underscores the critical need to understand and implement security best practices tailored to the unique challenges of cloud environments.

Central to understanding and navigating these challenges is the AWS shared responsibility model. AWS is responsible for delivering security of the cloud, including the security of underlying infrastructure and services. Customers are responsible for protecting their data, applications and resources running in the cloud. This model highlights the importance of proactive security measures at every phase of cloud migration and operation and helps ensure businesses maintain a strong security posture.

In this blog, we cover five best practices for securing AWS resources to help you gain a better understanding of how to protect your cloud environments as you build in the cloud.

Best Practice #1: Know All of Your Assets

Cloud assets are not limited to compute instances (aka virtual machines) — they extend to all application workloads spanning compute, storage, networking and an extensive portfolio of managed services.

Understanding and maintaining an accurate inventory of your AWS assets is foundational to securing your cloud environment. Given the dynamic nature of cloud computing, it's not uncommon for organizations to inadvertently lose track of assets running in their AWS accounts, which can lead to risk exposure and attacks on unprotected resources. In some cases, accounts created early in an organization’s cloud journey may not have the standard security controls that were implemented later on. In another common scenario, teams may forget about and unintentionally remove mitigations put in place to address application-specific exceptions, exposing those resources to potential attack.

To maintain adequate insight and awareness of all AWS assets in production, organizations should consider implementing the following:

• Conduct asset inventories: Use tools and processes that provide continuous visibility into all cloud assets. This can help maintain an inventory of public and private cloud resources and ensure all assets are accounted for and monitored. AWS Resource Explorer and Cost Explorer can help discover new resources as they’re provisioned.
• Implement asset tagging and management policies: Establish and enforce policies for tagging cloud resources. This practice aids in organizing assets based on criticality, sensitivity and ownership, making it easier to manage and prioritize security efforts across the cloud environment. In combination with the AWS Identity and Access Management (IAM) service, tagging can also be used to dynamically grant access to resources via attribute-based access control (ABAC).
• Integrate security tools for holistic visibility: Combine the capabilities of cloud security posture management (CSPM) with other security tools like endpoint detection and response (EDR) solutions. Integration of these tools can provide a more comprehensive view of the security landscape, enabling quicker identification of misconfigurations, vulnerabilities and threats across all AWS assets. AWS services including Trusted Advisor, Security Hub, GuardDuty, Config and Inspector provide actionable insights to help security and operations teams improve their security posture.

Best Practice #2: Enforce Multifactor Authentication (MFA) and Use Role-based Access Control in AWS

Stolen credentials pose a severe threat — whether they are user names and passwords or API key IDs and secrets — allowing adversaries to impersonate legitimate users and bypass identity-based access controls. This risk is exacerbated by scenarios where administrator credentials and hard-coded passwords are inadvertently stored in public-facing locations or within code repositories accessible online. Such exposures give attackers the opportunity to intercept live access keys, which they can use to authenticate to cloud services, posing as trusted users.

In cloud environments, as well as on-premises, organizations should adopt identity security best practices such as avoiding use of shared credentials, assigning least-privilege access policies and using a single source of truth through identity provider federation and single sign-on (SSO). AWS services such as IAM, Identity Center and Organizations can facilitate secure access to AWS services by supporting the creation of granular access policies, enabling temporary session tokens, and reporting on cross-account trusts and excessively permissive policies, thus minimizing the likelihood and impact of access key exposure. By implementing MFA in conjunction with SSO, role-based access and temporary sessions, organizations make it much harder for attackers to steal credentials and, more importantly, to effectively use them.

Best Practice #3: Automatically Scan AWS Resources for Excessive Public Exposure

The inadvertent public exposure and misconfiguration of cloud resources such as EC2 instances, Relational Database Service (RDS) and containers on ECS and EKS through overly permissive network access policies pose a risk to the security of cloud workloads. Such lapses can accidentally open the door to unauthorized access to vulnerable services, providing attackers with opportunities to exploit weaknesses for data theft, launching further attacks and moving laterally within the cloud environment.

To mitigate these risks and enhance cloud security posture, organizations should:

• Implement automated security audits: Utilize tools like AWS Trusted Advisor, AWS Config and AWS IAM Access Analyzer to continuously audit the configurations of AWS resources and identify and remediate excessive public exposure or misconfigurations.
• Secure AWS resources with proper security groups: Configure security groups for logical groups of AWS resources to restrict inbound and outbound traffic to only necessary and known IPs and ports. Whenever possible, use network access control lists (NACLs) to restrict inbound and outbound access across entire VPC subnets to prevent data exfiltration and block communication with potentially malicious external entities. Services like AWS Firewall Manager provide a single pane of glass for configuring network access for all resources in an AWS account using VPC Security Groups, Web Application Firewall (WAF) and Network Firewall.
• Collaborate across teams: Security teams should work closely with IT and DevOps to understand the necessary external services and configure permissions accordingly, balancing operational needs with security requirements.

Best Practice #4: Prioritize Alerts Based on Risk

Adversaries are becoming more skilled in attacking cloud environments, as evidenced by a 75% increase in cloud intrusions year-over-year in 2023. They are also growing faster: The average breakout time for eCrime operators to move laterally from one breached host to another host was just 62 minutes in 2023. The rise of new technologies, such as generative AI, has the potential to lower the barrier to entry for less-skilled adversaries, making it easier to launch sophisticated attacks. Amid these evolving trends, effective alert management is paramount.

Cloud services are built to deliver a constant stream of API audit and service access logs, but sifting through all of this data can overwhelm security analysts and detract from their ability to focus on genuine threats. While some logs may indicate high-severity attacks that demand immediate response, most tend to be informational and often lack direct security implications. Generating alerts based on this data can be imprecise, potentially resulting in many false positives, each of which require SecOps investigation. Alert investigations can consume precious time and scarce resources, leading to a situation where noisy security alerts prevent timely detection and effective response.

To navigate this complex landscape and enhance the effectiveness of cloud security operations, several best practices can be adopted to manage and prioritize alerts efficiently:

• Prioritize alerts strategically: Develop a systematic approach to capture and prioritize high-fidelity alerts. Implementing a triage process based on the severity of events helps focus resources on the most critical investigations.
• Create context around alerts: Enhance alert quality by enriching them with correlated data and context. This additional information increases confidence in the criticality of alerts, enabling more informed decision-making regarding their investigation.
• Integrate and correlate telemetry sources: Improve confidence in prioritizing or deprioritizing alerts by incorporating details from other relevant data sources or security tools. This combination allows for a more comprehensive understanding of the security landscape, aiding in the accurate identification of genuine threats.
• Outsource to a competent third party: For organizations overwhelmed by the volume of alerts, partnering with a managed detection and response (MDR) provider can be a viable solution. These partners can absorb the event burden, alleviating the bottleneck and allowing in-house teams to focus on strategic security initiatives.

Best Practice #5: Enable Comprehensive Logging

Adversaries that gain access to a compromised account can operate virtually undetected, limited only by the permissions granted to the account they used to break in. This stealthiness is compounded by the potential for log tampering and manipulation, where malicious actors may alter or delete log files to erase evidence of their activities. Such actions make it challenging to trace the adversary's movements, evaluate the extent of data tampering or theft, and understand the full scope of the security incident. The lack of a comprehensive audit trail due to disabled or misconfigured logging mechanisms hinders the ability to maintain visibility over cloud operations, making it more difficult to detect and respond to threats.

In response, organizations can:

• Enable comprehensive logging across the environment: Ensure AWS CloudTrail logs, S3 server access logs, Elastic Load Balancer (ELB) access logs, CloudFront logs and VPC flow logs are activated to maintain a detailed record of all activities and transactions.
• Ingest and alert on logs in your SIEM: Integrate and analyze logs within your security information and event management (SIEM) system to enable real-time alerts on suspicious activities. Retain logs even if immediate analysis capabilities are lacking, as they may provide valuable insights in future investigations.
• Ensure accuracy of logged data: For services behind proxies, like ELBs, ensure the logging captures original IP addresses from the X-Forwarded-For field to preserve crucial information for analysis.
• Detect and prevent log tampering: Monitor for API calls that attempt to disable logging and for unexpected changes in cloud services or account settings that could undermine logging integrity, in line with recommendations from the MITRE ATT&CK® framework. In addition, features such as MFA-Delete provide additional protection by requiring two-factor authentication to allow deletion of S3 buckets and critical data.

Additional Resources

• Read about common cloud misconfigurations in this CrowdStrike white paper: Seven Easily Exploited Cloud Misconfigurations.
• Download the CrowdStrike eBook, 8 Things Your Next SIEM Must Do, to understand the critical capabilities to look for when evaluating SIEM solutions.