You run an ad-supported photo-sharing website using S3 to serve photos to visitors of your site. At some point, you find out that other sites have been linking to photos on your site, causing loss to your business. What would be an effective method to mitigate this? 

Answer options:

A.Use CloudFront distributions for static content.
B.Store photos on an EBS volume of the web server.
C.Remove public read access and use presigned URL with expiration.
D.Block the IPs of the offending websites in Security Groups.

Correct Answer – C
When you create a presigned URL for your object, you must provide your security credentials, specify a bucket name, an object key, specify the HTTP method (GET to download the object) and expiration date and time. The presigned URLs are valid only for the specified duration.
The credentials that you can use to create a presigned URL include: 
IAM instance profile: Valid up to 6 hours.
AWS Security Token Service: Valid up to 36 hours when signed with permanent credentials, such as the credentials of the AWS account root user or an IAM user
IAM user: Valid up to 7 days when using AWS Signature Version 4
To create a presigned URL that`s valid for up to 7 days, first designate IAM user credentials (the access key and secret access key) to the SDK that you`re using. Then, generate a presigned URL using AWS Signature Version 4.
For more information on presigned URLs, please visit the link below.
https://docs.aws.amazon.com/AmazonS3/latest/dev/ShareObjectPreSignedURL.html