Serverless architectures are revolutionizing the way organizations procure and use enterprise technology. Until recently, information security architecture was relatively simple; you built a fortress around a server containing sensitive data, and deployed security solutions to control the flow of users accessing and leaving that server.
But how do you secure a server-less environment?
The Basics of Serverless Architecture
Serverless architecture is an emerging trend in cloud-hosted environments and refers to applications that significantly depend on third-party services (known as Backend-as-a-Service or “BaaS”) or on custom code that’s run in ephemeral containers (known as Function-as-a-Service or “FaaS”). And it is significantly more cost effective than buying or renting servers.
The rapid adoption of micro-efficiency-based pricing models (a.k.a PPU, or pay-per-use) pushes public cloud providers to introduce a business model that meets this requirement. Serverless computing helps providers optimize that model by dynamically managing the allocation of machine resources. As a result, organizations pay based on the actual amount of resources their applications consume, rather than ponying up for pre-purchased units of workload capacity (which is usually higher than what they utilize in reality).
What’s more, going serverless also frees developers and operators from the burdens of provisioning the cloud workload and infrastructure. There is no need to deploy operating systems and patch them, no need to install and configure web servers, and no need to set up or tune auto-scaling policies and systems.
Security Implications of Going Serverless
The new serverless model coerces a complete change in architecture – nano services of a lot of software ‘particles.’ The operational unit is set of function containers that execute REST API functions, which are invoked upon a relevant client-side event. These function instances are created, run and then terminated. During their run time, they receive, modify and send information that organizations want to monitor and protect. The protection should be dynamic and swift:
- There is no perimeter or OS to secure
- Agents and a persistent footprint become redundant.
- To optimize the business model, the solution must be scalable and ephemeral automation is the key to success
If we break down our application into components that run in a serverless model, the server that runs the APIs uses different layers of code to parse the requests, essentially enlarging the attack surface. However, this isn’t an enterprise problem anymore; it’s the cloud provider’s. Unfortunately, even they sometimes lag in patch management and hardening workloads. Will your DevOps read all of the cloud provider documentation in details? Most likely, they’ll go with generic permissions. If you want to do something right, you better do it yourself.
Serverless computing doesn’t eradicate all traditional security concerns. Application-level vulnerabilities can still be exploited—with attacks carried out by human hackers or bots—whether they are inherent in the FaaS infrastructure or in the developer function code.
When using a FaaS model, the lack of local persistent storage encourages data transfer between the function and the different persistent storage services (e.g., S3 and DynamoDB by AWS) instead. Additionally, each function eventually processes data received from storage, the client application or from a different function. Every time it’s moved, it becomes vulnerable to leakage or tampering.
In such an environment, it is impossible to track all potential and actual security events. One can’t follow each function’s operation to prevent it from accessing wrong resources. Visibility and forensics must be automated and perform real time contextual analysis. But the question is not whether to use serverless or not because it is more in/secure. Rather, the question is how to do it when your organization goes there.
A New Approach
Simply put, going serverless requires a completely different security approach—one that is dynamic, elastic, and real-time. The security components must be able to move around at the same pace as the applications, functions and data they protect.
First thing’s first: To help avoid code exploitation (which is what attacks boil down to), use encryption and monitor the function’s activity and data access so it has, by default, minimum permissions. Abnormal function behavior, such as expected access to data or non-reasonable traffic flow, must be analyzed.
Next, consider additional measures, like a web application firewall (WAF), to secure your APIs. While an API gateway can manage authentication and enforce JSON and XML validity checks, not all API gateways support schema and structure validation, nor do they provide full coverage of OWASP top 10 vulnerabilities like a WAF does. WAFs apply dozens of protection measures on both inbound and outbound traffic, which is parsed to detect protocol manipulations. Client-side inputs are validated and thousands of rules are applied to detect various injections attacks, XSS attacks, remote file inclusion, direct object references and many more.
In addition to detecting known attacks, for the purposes of zero-day attack protection and comprehensive application security, a high-end WAF allows strict policy enforcement where each function can have its own parameters white listed—the recommended approach when deploying a function processing sensitive data or mission-critical business logic.
And—this is critical—continue to mitigate for DDoS attacks. Going serverless does not eliminate the potential for falling susceptible to these attacks, which have changed dramatically over the past few years. Make no mistake: With the growing online availability of attack tools and services, the pool of possible attacks is larger than ever.