AWS Lambda simplifies server management, but security responsibilities can be confusing. Many assume AWS fully manages security, but that’s only partially correct.
AWS Lambda Security handles the “security of the cloud,” including infrastructure and runtime environments. You don’t need to manage servers or operating system updates.
However, “security in the cloud” – securing your code, managing secrets, and preventing vulnerabilities, is entirely your responsibility. Even a secure infrastructure can’t protect against insecure application practices.
In this guide, SotaTek will outline your security responsibilities and offer practical strategies to protect your serverless applications.
I. The Shared Responsibility Model in Serverless Context
AWS follows a clear division known as the Shared Responsibility Model, especially crucial when using AWS Lambda. Understanding this division helps you maintain robust security.
AWS Responsibilities: AWS manages the “security of the cloud,” handling all infrastructure-related security. This includes:
- Physical security of AWS data centers
- Network security (firewalls, networking hardware)
- Infrastructure maintenance and operations
- Compute resources, including Lambda runtimes and underlying operating system updates
Customer Responsibilities: Your role is securing what’s built “in the cloud,” specifically:
- Application code and dependencies
- Identity and Access Management (IAM) controls
- Configurations of AWS services used
- Management and rotation of secrets (passwords, API keys, certificates)
- Data encryption (both at rest and in transit)
- Monitoring, logging, and auditing your Lambda functions
- Compliance with relevant regulations and standards (e.g., GDPR, HIPAA)
In comparison, traditional VM or container environments (like Amazon EC2 or ECS) require users to handle additional infrastructure security tasks, such as operating system patching and detailed network configurations. Serverless simplifies your security responsibilities but requires focused attention on application-level protection.
Here’s a visual representation of the Shared Responsibility Model clearly outlining your role versus AWS’s role in security:
Shared Responsibility Model in Serverless Context
II. Top Security Risks in AWS Lambda Security (And How to Mitigate Them)
- Overly Permissive IAM Roles
Lambda functions are frequently deployed with IAM roles that grant broader permissions than necessary, breaching the principle of least privilege. This creates a serious AWS Lambda security risk: if the function becomes compromised, attackers could exploit these permissions to access or modify additional AWS services. To avoid this, always enforce strict IAM policies, limiting permissions precisely to the resources each function requires.
- Insecure Third-Party Dependencies
Open-source libraries included in Lambda functions might contain vulnerabilities. Outdated or compromised dependencies provide attackers with potential entry points. To mitigate this risk, employ scanning tools such as Amazon Inspector, Dependabot, or Snyk, regularly checking for known vulnerabilities and promptly updating any outdated dependencies.
- Event Injection & Input Validation Gaps
Lambda functions triggered by external events (e.g., API Gateway requests, S3 file uploads, SNS messages) may be susceptible to event injection attacks if inputs are not carefully validated. Risks include SQL Injection, Remote Code Execution, and Denial of Service (DoS) attacks. Mitigation involves sanitizing and validating inputs rigorously and adhering strictly to AWS Lambda security coding practices.
- Data Leakage Through Logging
Sensitive information, including personally identifiable information (PII) or secret credentials, could unintentionally appear in logs such as Amazon CloudWatch Logs. Unauthorized access to these logs can expose confidential data. Ensure sensitive information is scrubbed before logging and implement tight access controls on log data.
- Insecure Function Updates (CI/CD Risks)
Improper management of the Lambda deployment pipeline can result in the deployment of malicious or unintended code. Risks include compromised pipelines or accidental deployments. Mitigate these threats by following CI/CD best practices, signing deployment artifacts, and consistently using version control and auditing.
- Poor Secrets Management
Storing secrets, such as API keys or database credentials, directly within environment variables or code can lead to significant vulnerabilities. Secrets may leak through environment introspection or logging. Use secure solutions like AWS Secrets Manager or SSM Parameter Store, coupled with strict access controls, to manage secrets safely.
- Denial of Wallet (Uncontrolled Invocations)
Lambda’s ability to scale rapidly can become costly if abused or improperly managed, for instance through API request spamming. This can lead to unexpected and significant financial impact. Address this AWS Lambda security risk by applying rate limiting, throttling, and implementing AWS budgets and alarms to control resource usage.
- Lack of Monitoring & Auditing
Without adequate visibility into Lambda function behavior, detecting misuse or security breaches becomes challenging, leading to delayed detection of incidents or suspicious activities. To enhance visibility and response, enable AWS CloudTrail, utilize CloudWatch Metrics, and integrate your monitoring with AWS Security Hub.
III. Security Best Practices for AWS Lambda
1. IAM and Access Control
Proper access control is critical to AWS Lambda security. Always follow the principle of least privilege, assigning IAM roles that provide only the necessary permissions required for a Lambda function to operate. Use granular roles tailored explicitly for each Lambda function rather than broad or generic ones. AWS IAM Access Analyzer can help review IAM roles and policies regularly, identifying overly permissive roles and recommending adjustments. Additionally, leverage AWS Service Control Policies (SCPs) to set strict guardrails and prevent unauthorized actions across your organization’s AWS accounts.
2. Secrets & Configuration Management
Sensitive configuration data such as passwords, API keys, and certificates must never be stored directly in application code or environment variables. Instead, securely manage these secrets using AWS Secrets Manager or AWS Systems Manager Parameter Store. These services offer secure storage with built-in encryption, access control, and the ability to rotate secrets automatically, reducing the risk of secret exposure.
Sensitive configuration data such as passwords, API keys, and certificates must never be stored directly in application code or environment variables. Instead, securely manage these secrets using AWS Secrets Manager or AWS Systems Manager Parameter Store. These services offer secure storage with built-in encryption, access control, and the ability to rotate secrets automatically, reducing the risk of secret exposure.
