Essential AWS Security Best Practices for 2025

Implementing Least Privilege Access

The principle of least privilege means granting users and services only the permissions they need to perform their tasks—nothing more. This minimizes the potential damage from compromised credentials, insider threats, or misconfigured applications.

Start by auditing your current IAM policies. Remove overly permissive policies like AdministratorAccess except where absolutely necessary. Even administrators should use separate accounts for day-to-day work and only assume admin roles when needed.

Use IAM roles for EC2 instances and Lambda functions instead of embedding credentials in code or configuration files. Roles provide temporary credentials that are automatically rotated, eliminating the risk of long-lived credentials being exposed in code repositories or logs.

Implement permission boundaries to set the maximum permissions that IAM entities can have. This provides an additional layer of control, ensuring that even if someone creates a new policy, they cannot grant permissions beyond the boundary.

Rotate access keys regularly—at least every 90 days. Use AWS Config rules to automatically detect access keys that haven't been rotated and notify security teams. Better yet, eliminate access keys entirely where possible by using IAM roles and temporary credentials.

Remove unused credentials immediately. When employees leave or change roles, revoke their access within hours, not days. Use AWS IAM Access Analyzer to identify unused permissions and remove them.

Uptime.cx scans your IAM configuration and flags overly permissive policies, unused credentials, and other security risks. The platform provides specific recommendations for tightening permissions while maintaining functionality.

Enabling Multi-Factor Authentication

Multi-factor authentication (MFA) adds an essential layer of security to your AWS accounts. Even if credentials are compromised through phishing or data breaches, attackers cannot access your account without the second factor.

Enable MFA for all IAM users, especially those with administrative privileges. This should be non-negotiable for any user who can modify infrastructure, access sensitive data, or manage security settings.

Use hardware MFA devices (like YubiKey) for root accounts and critical admin users. Hardware tokens are more secure than virtual MFA apps because they're resistant to phishing and malware attacks.

For the root account, enable MFA immediately after account creation and store the MFA device in a secure physical location. The root account should only be used for tasks that absolutely require it, such as changing account settings or closing the account.

Enforce MFA through IAM policies that deny access to resources unless MFA is present. Create a policy that requires MFA for all API calls and attach it to all users and roles.

Consider using AWS SSO (now IAM Identity Center) with MFA enforcement. This provides a centralized way to manage access across multiple AWS accounts while enforcing MFA consistently.

Regularly audit MFA compliance. Use AWS Config rules or custom scripts to identify users without MFA enabled and automatically notify them or their managers.

Network Segmentation and Security Groups

Proper network segmentation limits the blast radius of security incidents. If an attacker compromises one component, network segmentation prevents them from easily moving laterally to other systems.

Use separate VPCs to isolate different environments (production, staging, development) and different applications. This provides strong isolation and makes it easier to apply different security policies to each environment.

Within each VPC, use multiple subnets to segment different tiers of your application. Place web servers in public subnets, application servers in private subnets, and databases in isolated private subnets with no internet access.

Configure security groups to allow only necessary traffic. Follow the principle of deny-by-default, explicitly allowing only required ports and protocols. Never use 0.0.0.0/0 as a source for inbound rules except for public-facing load balancers.

Use security group references instead of IP addresses where possible. For example, allow your application tier security group to access your database tier security group on port 3306. This makes rules more maintainable and reduces errors.

Implement network ACLs as an additional layer of defense. While security groups are stateful and sufficient for most use cases, NACLs provide stateless filtering at the subnet level, adding defense in depth.

Use private subnets for databases and application servers that don't need direct internet access. Place only load balancers and bastion hosts in public subnets. This significantly reduces your attack surface.

Regularly review security group rules to remove unnecessary access. Uptime.cx identifies overly permissive security groups (like those allowing 0.0.0.0/0 on sensitive ports) and suggests improvements based on actual traffic patterns.

Enabling Logging and Monitoring

You can't protect what you can't see. Comprehensive logging and monitoring are essential for detecting security incidents, investigating breaches, and meeting compliance requirements.

Enable CloudTrail for all regions to log all API calls made in your account. CloudTrail provides a complete audit trail of who did what, when, and from where. This is invaluable for security investigations and compliance audits.

Configure CloudTrail to deliver logs to a dedicated S3 bucket in a separate security account. Enable MFA Delete and object lock on this bucket to prevent attackers from covering their tracks by deleting logs.

Use VPC Flow Logs to monitor network traffic patterns and identify potential security issues. Flow logs can reveal port scanning, data exfiltration attempts, and communication with known malicious IP addresses.

Enable S3 access logging for buckets containing sensitive data. This provides detailed records of all requests made to your buckets, helping you detect unauthorized access attempts.

Set up CloudWatch alarms for critical security events: root account usage, failed login attempts, unauthorized API calls, changes to security groups, and IAM policy modifications. Configure these alarms to notify your security team immediately.

Use AWS Config to continuously monitor and record your AWS resource configurations. Config can detect when resources drift from approved configurations and automatically remediate or alert on violations.

Consider using AWS GuardDuty for intelligent threat detection. GuardDuty uses machine learning to analyze CloudTrail logs, VPC Flow Logs, and DNS logs to identify suspicious activity like cryptocurrency mining, credential compromise, and communication with known malicious IPs.

Implement centralized log aggregation using CloudWatch Logs or a third-party SIEM solution. Centralized logging makes it easier to correlate events across multiple accounts and services, improving your ability to detect sophisticated attacks.

Encrypting Data at Rest and in Transit

Encryption protects your data even if storage media is compromised or intercepted. AWS provides multiple encryption options, and there's rarely a good reason not to use them.

Enable encryption for all EBS volumes, including root volumes. EBS encryption uses AES-256 and has negligible performance impact on modern instance types. You can enable encryption by default for all new volumes in your account settings.

Encrypt all S3 buckets using server-side encryption. Use SSE-S3 for general use cases, SSE-KMS when you need audit trails and key rotation, or SSE-C when you need to manage keys yourself. Enable default encryption on all buckets to ensure new objects are automatically encrypted.

Enable encryption for RDS databases and their snapshots. RDS encryption uses AES-256 and is transparent to applications. Note that you cannot enable encryption on an existing unencrypted database—you must create an encrypted snapshot and restore it.

Use AWS KMS to manage encryption keys centrally. KMS provides audit trails of key usage, automatic key rotation, and fine-grained access control. Create separate KMS keys for different data classifications or compliance requirements.

Enable automatic key rotation for KMS keys. AWS automatically rotates KMS keys annually, generating new cryptographic material while keeping the same key ID. This reduces the risk from long-term key exposure.

Enforce HTTPS for all web traffic using Application Load Balancers or CloudFront. Configure your load balancers to redirect HTTP to HTTPS automatically. Use AWS Certificate Manager to provision and manage SSL/TLS certificates at no cost.

Disable insecure protocols like SSLv3, TLS 1.0, and TLS 1.1. Use security policies that enforce TLS 1.2 or higher. Most modern clients support TLS 1.2, and using older protocols exposes you to known vulnerabilities.

For highly sensitive data, consider client-side encryption where data is encrypted before it leaves your application. This provides an additional layer of protection and ensures that even AWS cannot access your data in plaintext.

Securing S3 Buckets

S3 bucket misconfigurations are one of the most common causes of data breaches. Securing S3 buckets requires multiple layers of protection and constant vigilance.

Block public access at the account level using S3 Block Public Access settings. This prevents any bucket in your account from being made public, even if someone explicitly tries to configure public access. Enable all four Block Public Access settings unless you have a specific need for public buckets.

For buckets that must be public (like static website hosting), use bucket policies to restrict access as much as possible. Consider using CloudFront with Origin Access Identity instead of making buckets directly public.

Enable S3 versioning on buckets containing important data. Versioning protects against accidental deletion and allows you to recover from ransomware attacks by restoring previous versions of objects.

Use S3 Object Lock for compliance and data retention requirements. Object Lock prevents objects from being deleted or modified for a specified retention period, protecting against insider threats and ransomware.

Implement least privilege access using bucket policies and IAM policies. Grant access only to specific principals for specific actions. Use conditions to further restrict access based on IP address, VPC endpoint, or MFA.

Enable S3 access logging and regularly review logs for suspicious activity. Look for unusual access patterns, access from unexpected IP addresses, or large numbers of 403 (forbidden) errors that might indicate scanning attempts.

Use AWS Macie to automatically discover and classify sensitive data in S3. Macie uses machine learning to identify PII, financial data, and credentials stored in S3 buckets, helping you apply appropriate protections.

Implementing Security Automation

Manual security processes don't scale and are prone to human error. Automation ensures consistent security posture and rapid response to threats.

Use AWS Config Rules to automatically detect security violations. Create rules for common security requirements: encrypted EBS volumes, MFA on root account, restricted security group rules, and S3 bucket encryption.

Implement automatic remediation for common security issues. AWS Config can trigger Lambda functions or Systems Manager automation documents to automatically fix violations, like removing overly permissive security group rules or enabling encryption.

Use AWS Security Hub to aggregate security findings from multiple services (GuardDuty, Inspector, Macie, Config) into a single dashboard. Security Hub also provides automated compliance checks against standards like CIS AWS Foundations Benchmark.

Implement infrastructure as code (IaC) with security scanning. Use tools like cfn-nag or Checkov to scan CloudFormation templates and Terraform code for security issues before deployment. This shifts security left, catching issues before they reach production.

Create Lambda functions to automatically respond to security events. For example, automatically revoke IAM credentials when GuardDuty detects credential compromise, or isolate EC2 instances when suspicious activity is detected.

Use AWS Systems Manager Session Manager instead of SSH for accessing EC2 instances. Session Manager provides secure access without opening inbound ports, logs all session activity, and integrates with IAM for access control.

Implement automated vulnerability scanning using Amazon Inspector. Inspector automatically assesses EC2 instances and container images for software vulnerabilities and network exposure, providing prioritized findings.

Incident Response Planning

Despite best efforts, security incidents will occur. Having a well-defined incident response plan minimizes damage and recovery time.

Create an incident response plan that defines roles, responsibilities, and procedures for different types of security incidents. Document escalation paths and contact information for key personnel.

Establish a security incident response team with members from security, operations, legal, and communications. Ensure team members are trained and conduct regular tabletop exercises to practice incident response.

Use AWS Systems Manager Incident Manager to coordinate incident response. Incident Manager provides automated escalation, runbook execution, and post-incident analysis capabilities.

Implement forensic readiness by enabling comprehensive logging and creating AMI snapshots of critical systems. In the event of an incident, you'll need this data for investigation and potential legal proceedings.

Create runbooks for common security scenarios: compromised credentials, data exfiltration, DDoS attacks, and ransomware. Runbooks should provide step-by-step procedures for containment, eradication, and recovery.

Practice incident response through regular simulations. Use AWS Fault Injection Simulator or manual exercises to simulate security incidents and test your team's response.

Establish relationships with AWS support and law enforcement before an incident occurs. Know how to engage AWS security teams and when to involve law enforcement.

Conduct post-incident reviews after every security event. Document what happened, how it was detected, how it was handled, and what can be improved. Use these lessons to strengthen your security posture.