Lambda functions typically refer to AWS Lambda, which is a serverless computing service provided by Amazon Web Services (AWS). AWS Lambda allows you to run code in response to events and triggers without the need to provision or manage servers. It’s commonly used for building scalable and cost-effective applications.

When it comes to Lambda security, there are several aspects to consider to ensure your functions are secure:

1. Authentication and Authorization: Use AWS Identity and Access Management (IAM) roles and policies to control who has access to your Lambda functions and the resources they interact with. Assign the least privilege principle, giving users and functions only the permissions they need.

2. Input Validation: Validate and sanitize input data to prevent injection attacks, data manipulation, and other security vulnerabilities.

3. Environment Variables: Avoid hardcoding sensitive information like API keys or credentials within your code. Instead, use Lambda’s environment variables to securely store and retrieve such sensitive information.

4. Encryption: If your Lambda functions handle sensitive data, consider using encryption for both data at rest and data in transit. AWS Key Management Service (KMS) can be used to manage encryption keys.

5. VPC and Network Security: Place your Lambda functions within a Virtual Private Cloud (VPC) to control their network access and enhance security. Use security groups and network ACLs to restrict inbound and outbound traffic.

6. Logging and Monitoring: Enable AWS CloudWatch Logs to capture logs from your Lambda functions. Set up CloudWatch Alarms to be alerted about unusual behavior or errors. Monitoring can help you quickly identify and respond to security incidents.

7. Code Dependencies: Regularly update and patch the libraries and dependencies your Lambda functions use to avoid vulnerabilities present in outdated versions.

8. Execution Role Policies: Assign the Lambda execution role only the permissions needed for your function to perform its intended actions. Avoid giving excessive permissions that might be exploited.

9. Secure Coding Practices: Follow secure coding practices to prevent common vulnerabilities like cross-site scripting (XSS), SQL injection, and more.

10. Immutable Deployments: Deploy your Lambda functions using immutable deployment practices. This ensures that the code you deploy remains unchanged and secure throughout its lifecycle.

11. Error Handling: Implement proper error handling and fail gracefully to prevent exposing sensitive information in error messages.

12. Resource Limits: Configure resource limits for your Lambda functions to prevent excessive resource consumption or potential abuse.

Remember that security is a continuous process, and it’s essential to stay updated with AWS security best practices, new features, and any emerging threats. Regularly audit and assess your Lambda functions’ security posture to ensure they remain protected over time.