Is it safe to use AWS S3 after all the news about data breaches?

Post • 4 min read
There has recently been a lot of news about data breaches on AWS S3 (Simple Storage System). Sensitive data, passwords and access credentials have been exposed to the whole world. For many, this might have led to the assumption that S3 itself would be insecure and it would be better to avoid using it. The truth is quite the opposite. S3 is totally suitable for storing even sensitive data. As in most cases, the S3 data breaches happened because of human error and misconfiguration, not because of security issues in the service itself.

What is S3 and how do data leaks happen?

So, let’s rewind a bit to get to the bottom of this. What is S3? It’s a managed, highly available and highly scalable object storage which is used over an API. Typically, you access this API with secure credentials created for an AWS user. You create “Buckets” and store your objects (files) inside these buckets. You don’t provision any storage beforehand; you just use as much as you like and pay for what you use. S3 was one of the first services introduced by AWS over 10 years ago and has been truly battle-tested on performance, security and availability. It’s also one of the backbone services of AWS and is widely used by other AWS services too. So how do data leaks happen? The simple reason is that you can make your buckets or single objects inside a bucket public. This means that anyone with the correct URL can access that object. This is a very useful feature for sharing files to your users and it is widely used to deliver the static content of web applications. But no data inside S3 is ever public by default. You need to separately enable this. There are multiple ways to make objects public on bucket and object level including Bucket policies, Bucket ACLs and Object ACLs. This can be confusing but luckily AWS has recently introduced extremely good indication in the Management Console on what data is public and why. It takes some effort and lack of understanding to get this wrong if you make use of this information. In addition to this, there are AWS services like AWS Config and Trusted Advisor that can also give you reports on your publicly open buckets.

Why do data leaks happen then?

There are few typical explanations for this:
  1. The main reason is the lack of governance in the organisation. Governance and standards should be in place to ensure that best practices of the platform, as well as company cloud policies, are followed. This includes access management of S3 buckets.
  2. Without proper AWS knowledge, developers or operators don’t understand how S3 works. They might open the buckets for public access just to be able to access the data from an application that could use access credentials instead. They might not understand that “public” means “public”. It requires understanding of AWS Identity and Access Management together with IAM policies and Bucket policies to get this right.
  3. It might be that some “convenient” pre-created S3 Bucket is used for multiple different types of data including sensitive data and the bucket is exposed publicly for the original use case. Again, it comes down to understanding how S3 works.
  4. Some 3rd party tools that upload files to S3 might have default or optional settings to make the objects' public with an object ACL during the upload. In some cases, it might be that these tools are used and that’s the reason for the public access. Again, understanding how S3 and AWS in general works would mitigate this.

Understand the AWS platform

To recap, it all comes down to basic training and understanding on the AWS platform. And this is not limited to S3. In some cases, there’s public access to services because AWS networking, firewall and access management concepts are not understood correctly. It might be that you don’t have proper authentication settings in place in the actual AWS accounts. Or it might be just that general security principles like proper patching plan are not followed. There’s a lot to learn when starting a cloud journey and a proper cloud foundation must be built for networking and security together with educating people on how to use the services. Luckily, we are here to help you out with all of that!
Juho Jantunen

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