Access logging (for example, load balancers, CloudFront)

What is the purpose of enabling access logs in load balancers such as AWS Elastic Load Balancing (ELB)?

Access logs for load balancers are intended to capture detailed information about all requests sent to the load balancer. They are beneficial for analyzing traffic patterns, troubleshooting issues, improving security, and understanding user behavior. By analyzing these logs, you can determine the source IP, request paths, latencies, and backend response times which can help in identifying any potential performance bottlenecks or security threats.

How often are access logs delivered to the specified S3 bucket when using Amazon CloudFront?

Access logs for Amazon CloudFront are usually delivered to the Amazon S3 bucket within several hours of the requests that generated them. There is no fixed schedule, as delivery timing may vary based on the log file size and number of requests.

Can access logging be used to monitor the health of targets behind a load balancer in AWS?

While access logs are not primarily designed for health monitoring, they do provide detailed request data that could indicate issues with targets. For health monitoring, AWS provides a more specific feature called health checks, which automatically check the health of the targets to ensure traffic is routed only to healthy instances. Nevertheless, access logs can be useful for post-analysis if there are issues noted in health checks.

How can you secure access to your load balancer access logs in S3?

You can secure access logs by using AWS Identity and Access Management (IAM) policies to restrict access, enable S3 bucket encryption for the logs at rest, enforce the use of secure transport (HTTPS) to access the logs, and optionally use AWS Key Management Service (KMS) for encryption key management. It’s also advised to regularly audit who has access permissions using AWS Access Analyzer.

Are there any additional costs associated with CloudFront or ELB access logging? If so, what are they?

There is no additional cost for enabling access logging itself; however, standard Amazon S3 charges apply for the storage and access of the log files, including PUT requests to write the access logs and data transfer fees for log file retrieval. It is important to take these costs into consideration when utilizing extensive logging.

What are the key differences between access logs for Amazon CloudFront and logs for AWS Elastic Load Balancing?

Amazon CloudFront logs provide detailed records about each user request for content delivered through the CDN, which includes data like IP address, query strings, and HTTP response codes for global requests directed at the content delivery network. ELB access logs, on the other hand, capture detailed information about requests sent to the load balancer itself, including the backend instance responses, primarily focusing on the application level and not the content delivery aspect.

In AWS, how can you analyze access logs efficiently to gain insights about your application’s performance and users’ behavior?

Efficient analysis of access logs can be accomplished by utilizing AWS native tools like Amazon Athena to query the log data directly from S3 using SQL. You can also integrate with Amazon ElasticSearch Service for real-time analysis, or employ third-party log analysis tools and services. Using such tools allows you to create dashboards, set alarms, and perform deep analytics to understand application performance and user behavior.

How can access logs be used to mitigate security threats in AWS?

Access logs are useful for forensic analysis in the case of a security breach, as they provide detailed request-level data. They can be scrutinized for suspicious patterns, such as repeated failed login attempts or unusual traffic spikes. Additionally, integrating access logs with AWS services like AWS Lambda and Amazon CloudWatch can automate responses to certain threat patterns, such as triggering AWS WAF rules or scaling policies in response to DoS attacks.

Can data contained in AWS access logs be redacted or masked for privacy or compliance reasons before storing it?

AWS does not provide built-in features to redact or mask data in the access logs before storage. To comply with privacy regulations such as GDPR, you need to implement a custom solution to process and potentially remove sensitive data either before it is written to the log or through a post-processing step after the log is stored.

In Amazon CloudFront, what kind of information does the ‘cs-uri-stem’ field in access logs indicate?

In Amazon CloudFront access logs, the ‘cs-uri-stem’ field indicates the portion of the request URI, which represents the path to the requested object in the distribution. This information is crucial for understanding what content is being requested most frequently and can assist in optimizing and managing content caching.

Is it possible to enable access logging for a pre-existing load balancer or CloudFront distribution, and if so, how?

Yes, it is possible to enable access logging for existing load balancers and CloudFront distributions. For a load balancer, access logging can be enabled through the AWS Management Console, AWS CLI, or the ELB API by modifying the attributes of the load balancer. For CloudFront, you modify the distribution settings to specify the S3 bucket where logs should be stored.

How long are access logs retained in an S3 bucket, and how can retention policies be managed?

By default, access logs stored in an S3 bucket are retained indefinitely until they are explicitly deleted by the bucket owner. To manage retention policies, you can use S3 Lifecycle policies to automatically archive or delete log files after a certain period, which can help control costs and comply with your organization’s data retention policies.